Strontianite
Encyclopedia
Strontianite is an important raw material for the extraction of strontium
. It is a rare carbonate mineral and one of only a few strontium minerals. It is a member of the aragonite group.
Aragonite group members:
The ideal formula of strontianite is SrCO3, with molar mass
147.63 g, but calcium
Ca can substitute for up to 27% of the strontium Sr cations
, and barium
Ba up to 3.3 %.
The mineral was named in 1791 for the locality, Strontian
, Argyllshire, Scotland, where the element strontium
had been discovered the previous year. Although good mineral specimens of strontianite are rare, strontium is a fairly common element
, with abundance in the Earth's crust
of 370 parts per million by weight, 87 parts per million by moles
, much commoner than copper
with only 60 parts per million by weight, 19 by moles.
Strontium is never found free in nature. The principal strontium ores are celestine
SrSO4 and strontianite SrCO3. The main commercial process for strontium metal production is reduction
of strontium oxide
with aluminium
.
mineral, belonging to the most symmetrical class in this system, 2/m 2/m 2/m, whose general form is a rhombic
dipyramid
. The space group
is Pmcn. There are four formula units per unit cell (Z = 4) and the unit cell parameters are a = 5.1 Å, b = 8.4 Å, c = 6.0 Å.
with aragonite
. When the CO3 group is combined with large divalent
cations
with ionic radii
greater than 1.0 Å, the radius ratios generally do not permit stable 6-fold coordination
. For small cations the structure is rhombohedral
, but for large cations it is orthorhombic
. This is the aragonite structure type with space group
Pmcn. In this structure the CO3 groups lie perpendicular to the c axis
, in two structural planes, with the CO3 triangular groups of one plane pointing in opposite directions to those of the other. These layers are separated by layers of cations.
The CO3 group is slightly non-planar; the carbon
atom
lies 0.007 Å out of the plane of the oxygen
atoms. The groups are tilted such that the angle between a plane drawn through the oxygen atoms and a plane parallel to the a-b unit cell plane is 2°40’.
. Crystals are short prismatic
parallel to the c axis and often acicular
. Calcium
-rich varieties often show steep pyramidal
forms. Crystals may be pseudo hexagonal due to equal development of different forms. Prism faces are striated horizontally. The mineral also occurs as columnar to fibrous, granular or rounded masses.
, resinous on broken surfaces, and a white streak
.
It is a biaxial(-) mineral. The direction perpendicular to the plane containing the two optic axes
is called the optical direction Y. In strontianite Y is parallel to the b crystal axis. The optical direction Z lies in the plane containing the two optic axes and bisects the acute angle between them. In strontianite Z is parallel to the a crystal axis. The third direction X, perpendicular both to Y and to Z, is parallel to the c crystal axis. The refractive indices
are close to nα = 1.52, nβ = 1.66, nγ = 1.67, with different sources quoting slightly different values:
The maximum birefringence
δ is 0.15 and the measured value of 2V
is 7°, calculated 12° to 8°.
If the colour of the incident light is changed, then the refractive indices are modified, and the value of 2V changes. This is known as dispersion of the optic axes. For strontianite the effect is weak, with 2V larger for violet light than for red light r < v.
. It fluoresces bright yellowish white under shortwave, mediumwave and longwave ultraviolet
radiation. If the luminescence persists after the ultraviolet source is switched off the sample is said to be phosphorescent
. Most strontianite phosphoresces a strong, medium duration, yellowish white after exposure to all three wavelengths. It is also fluorescent and phosphorescent in X-rays and electron beams
. All materials will glow red hot if they are heated to a high enough temperature (provided they do not decompose first); some materials become luminescent at much lower temperatures, and this is known as thermoluminescence
. Strontianite is sometimes thermoluminescent.
is nearly perfect parallel to one set of prism faces, {110}
, and poor on {021}. Traces of cleavage have been observed on {010}.
Twinning
is very common, with twin plane {110}. The twins are usually contact twins; in a contact twin the two individuals appear to be reflections of each other in the twin plane. Penetration twins of strontainite are rarer; penetration twins are made up of interpenetrating individuals that are related to each other by rotation about a twin axis. Repeated twins are made up of three or more individuals twinned according to the same law. If all the twin planes are parallel then the twin is polysynthetic, otherwise it is cyclic. In strontianite repeated twinning forms cyclic twins with three or four individuals, or polysynthetic twins.
The mineral is brittle, and breaks with a subconchoidal to uneven fracture. It is quite soft, with a Mohs hardness of 3½, between calcite
and fluorite
. The specific gravity
of the pure end member with no calcium substituting for strontium is 3.78, but most samples contain some calcium, which is lighter than strontium, giving a lower specific gravity, in the range 3.74 to 3.78. Substitutions of the heavier ions barium
and/or lead
increase the specific gravity, although such substitutions are never very abundant. Strontianite is soluble in dilute hydrochloric acid
HCl and it is not radioactive
.
in limestone
, marl
, and chalk
, and in geodes and concretions. It occurs rarely in hydrothermal metallic veins but is common in carbonatite
s. It most likely crystallises at or near 100 °C. Its occurrence in open vugs
and veins suggests crystallisation at very low pressures, probably at most equal to the hydrostatic pressure of the ground water. Under appropriate conditions it alters to celestine
SrSO4, and it is itself found as an alteration from celestine. These two minerals are often found in association, together with baryte, calcite
, harmotome
and sulfur
.
is Strontian
, North West Highlands (Argyllshire), Scotland
, UK. The type material occurred in veins in gneiss
.
Other UK localities include Brownley Hill Mine (Bloomsberry Horse Level), Nenthead, Alston Moor
District, North Pennines, North and Western Region (Cumberland), Cumbria, England, associated with a suite of primary mierals (bournonite
, millerite
and ullmannite
) which are not common in other Mississippi Valley-type deposits
.
, Québec.
Strontianite is very common at the Francon Quarry, in a great variety of habits. It is a late stage mineral, sometimes found as multiple generations. It is found as translucent to opaque, white to pale yellow or beige generally smooth surfaced spheroids, hemispheres and compact spherical and botryoidal aggregates to 10 cm in diameter, and as spheres consisting of numerous radiating acicular crystals, up to 1 cm across. Also as tufts, parallel bundles, and sheaf-like clusters of fibrous to acicular crystals, and as white, finely granular porcelaneous and waxy globular aggregates. Transparent, pale pink, columnar to tabular sixling twins up to 1 cm in diameter have been found, and aggregates of stacked stellate sixling twins consisting of transparent, pale yellow tabular crystals.
Another Canadian occurrence is at Nepean
, Ontario, in vein deposits in limestone
.
, and it is also found with zeolites at Oberschaffhausen, Bötzingen
, Kaiserstuhl, Baden-Württemberg.
SrSO4, gypsum
and phosphatic nodules in clay
.
District, with celestine
in a lead
-silver
deposit.
mine (Kirovsky Mine; Kirovskii Mine; Kirov Mine), Kukisvumchorr Mt, Khibiny Massif
, Kola Peninsula
, Murmanskaja Oblast', Northern Region, in late hydrothermal assemblages in cavities in pegmatites, associated with kukharenkoite-(La), microcline
, albite
, calcite
, nenadkevichite
, hilairite, catapleiite, donnayite-(Y)
, synchysite-(Ce), pyrite
and others.
It also occurs at Yukspor Mountain, Khibiny Massif, Kola Peninsula, Murmanskaja Oblast', Northern Region, in an aegerine-natrolite
-microcline
vein in foyaite, associated with aegirine
, anatase
, ancylite-(Ce), barylite, catapleiite, cerite-(Ce), cerite-(La), chabazite-(Ca), edingtonite
, fluorapatite
, galena
, ilmenite
, microcline
, natrolite
, sphalerite
and vanadinite
. At the same locality it was found in alkaline pegmatite
veins associated with clinobarylite, natrolite
, aegirine
, microcline
, catapleiite, fluorapatite
, titanite
, fluorite
, galena
, sphalerite
, annite
, astrophyllite
, lorenzenite
, labuntsovite-Mn, kuzmenkoite-Mn, cerite-(Ce), edingtonite
, ilmenite
and calcite
.
and Texas
, strontianite occurs with celestine
in calcite
cap rock of salt domes.
At the Minerva Number 1 Mine (Ozark-Mahoning Number 1 Mine) Ozark-Mahoning Group, Cave-in-Rock, Illinois
, in the Kentucky Fluorspar District, Hardin County
strontanite occurs as white, brown or rarely pink tufts and bowties of acicular crystals with slightly curved terminations.
In the Silurian
Lockport
Group, Central and Western New York
strontianite is observed in cavities in eastern Lockport, where it occurs as small white radiating sprays of acicular crystals.
In Schoharie County, New York, it occurs in geodes and veins with celestine
and calcite
in limestone
, and in Mifflin County, Pennsylvania, it occurs with aragonite
, again in limestone
.
Strontium
Strontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and...
. It is a rare carbonate mineral and one of only a few strontium minerals. It is a member of the aragonite group.
Aragonite group members:
- aragoniteAragoniteAragonite is a carbonate mineral, one of the two common, naturally occurring, crystal forms of calcium carbonate, CaCO3...
CaCO3 - witheriteWitheriteWitherite is a barium carbonate mineral, BaCO3, in the aragonite group. Witherite crystallizes in the orthorhombic system and virtually always is twinned. The mineral is colorless, milky white, grey, pale yellow, green, to pale brown. The specific gravity is 4.3, which is high for a translucent...
BaCO3 - strontianite SrCO3
- cerussiteCerussiteCerussite is a mineral consisting of lead carbonate , and an important ore of lead. The name is from the Latin cerussa, white lead. Cerussa nativa was mentioned by Conrad Gessner in 1565, and in 1832 F. S. Beudant applied the name cruse to the mineral, whilst the present form, cerussite, is due to...
PbCO3
The ideal formula of strontianite is SrCO3, with molar mass
Molar mass
Molar mass, symbol M, is a physical property of a given substance , namely its mass per amount of substance. The base SI unit for mass is the kilogram and that for amount of substance is the mole. Thus, the derived unit for molar mass is kg/mol...
147.63 g, but calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
Ca can substitute for up to 27% of the strontium Sr cations
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
, and barium
Barium
Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Barium is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with...
Ba up to 3.3 %.
The mineral was named in 1791 for the locality, Strontian
Strontian
Strontian is the main village in Sunart, an area in western Lochaber, Highland, Scotland, on the A861 road. It lies on the north shore of Loch Sunart, close to the head of the loch...
, Argyllshire, Scotland, where the element strontium
Strontium
Strontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and...
had been discovered the previous year. Although good mineral specimens of strontianite are rare, strontium is a fairly common element
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
, with abundance in the Earth's crust
Crust (geology)
In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle...
of 370 parts per million by weight, 87 parts per million by moles
Mole (unit)
The mole is a unit of measurement used in chemistry to express amounts of a chemical substance, defined as an amount of a substance that contains as many elementary entities as there are atoms in 12 grams of pure carbon-12 , the isotope of carbon with atomic weight 12. This corresponds to a value...
, much commoner than copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
with only 60 parts per million by weight, 19 by moles.
Strontium is never found free in nature. The principal strontium ores are celestine
Celestine
Celestine may refer to:Popes of the Roman Catholic Church:* Pope Celestine I * Pope Celestine II * Pope Celestine III * Pope Celestine IV * Pope Celestine V *Antipope Celestine II Other...
SrSO4 and strontianite SrCO3. The main commercial process for strontium metal production is reduction
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....
of strontium oxide
Strontium oxide
Strontium oxide or strontia, SrO, is formed when strontium reacts with oxygen. Burning strontium in air results in a mixture of strontium oxide and strontium nitride. It also forms from the decomposition of strontium carbonate SrCO3...
with aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
.
Unit cell
Strontianite is an orthorhombicOrthorhombic crystal system
In crystallography, the orthorhombic crystal system is one of the seven lattice point groups. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a rectangular base and height , such that a,...
mineral, belonging to the most symmetrical class in this system, 2/m 2/m 2/m, whose general form is a rhombic
Rhombus
In Euclidean geometry, a rhombus or rhomb is a convex quadrilateral whose four sides all have the same length. The rhombus is often called a diamond, after the diamonds suit in playing cards, or a lozenge, though the latter sometimes refers specifically to a rhombus with a 45° angle.Every...
dipyramid
Bipyramid
An n-gonal bipyramid or dipyramid is a polyhedron formed by joining an n-gonal pyramid and its mirror image base-to-base.The referenced n-gon in the name of the bipyramids is not an external face but an internal one, existing on the primary symmetry plane which connects the two pyramid halves.The...
. The space group
Space group
In mathematics and geometry, a space group is a symmetry group, usually for three dimensions, that divides space into discrete repeatable domains.In three dimensions, there are 219 unique types, or counted as 230 if chiral copies are considered distinct...
is Pmcn. There are four formula units per unit cell (Z = 4) and the unit cell parameters are a = 5.1 Å, b = 8.4 Å, c = 6.0 Å.
Structure
Strontianite is isostructuralIsostructural
The term isostructural is used for chemical compounds that have similar chemical structures, and also with the meaning of isomorphous when used in relation to crystal structures...
with aragonite
Aragonite
Aragonite is a carbonate mineral, one of the two common, naturally occurring, crystal forms of calcium carbonate, CaCO3...
. When the CO3 group is combined with large divalent
Divalent
In chemistry, a divalent ion or molecule has a valence of two and thus can form two bonds with other ions or molecules. An older term for divalent is bivalent....
cations
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
with ionic radii
Ionic radius
Ionic radius, rion, is the radius of an atom's ion. Although neither atoms nor ions have sharp boundaries, it is important to treat them as if they are hard spheres with radii such that the sum of ionic radii of the cation and anion gives the distance between the ions in a crystal lattice...
greater than 1.0 Å, the radius ratios generally do not permit stable 6-fold coordination
Coordination number
In chemistry and crystallography, the coordination number of a central atom in a molecule or crystal is the number of its nearest neighbours. This number is determined somewhat differently for molecules and for crystals....
. For small cations the structure is rhombohedral
Rhombohedron
In geometry, a rhombohedron is a three-dimensional figure like a cube, except that its faces are not squares but rhombi. It is a special case of a parallelepiped where all edges are the same length....
, but for large cations it is orthorhombic
Orthorhombic crystal system
In crystallography, the orthorhombic crystal system is one of the seven lattice point groups. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a rectangular base and height , such that a,...
. This is the aragonite structure type with space group
Space group
In mathematics and geometry, a space group is a symmetry group, usually for three dimensions, that divides space into discrete repeatable domains.In three dimensions, there are 219 unique types, or counted as 230 if chiral copies are considered distinct...
Pmcn. In this structure the CO3 groups lie perpendicular to the c axis
Crystal structure
In mineralogy and crystallography, crystal structure is a unique arrangement of atoms or molecules in a crystalline liquid or solid. A crystal structure is composed of a pattern, a set of atoms arranged in a particular way, and a lattice exhibiting long-range order and symmetry...
, in two structural planes, with the CO3 triangular groups of one plane pointing in opposite directions to those of the other. These layers are separated by layers of cations.
The CO3 group is slightly non-planar; the carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
atom
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
lies 0.007 Å out of the plane of the oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
atoms. The groups are tilted such that the angle between a plane drawn through the oxygen atoms and a plane parallel to the a-b unit cell plane is 2°40’.
Crystal form
Strontianite occurs in several different habitsCrystal habit
Crystal habit is an overall description of the visible external shape of a mineral. This description can apply to an individual crystal or an assembly of crystals or aggregates....
. Crystals are short prismatic
Prism (geometry)
In geometry, a prism is a polyhedron with an n-sided polygonal base, a translated copy , and n other faces joining corresponding sides of the two bases. All cross-sections parallel to the base faces are the same. Prisms are named for their base, so a prism with a pentagonal base is called a...
parallel to the c axis and often acicular
Acicular (crystal habit)
Acicular, in mineralogy, refers to a crystal habit composed of a radiating mass of slender, needle-like crystals. Minerals with this habit tend to be fragile and complete, undamaged specimens can be uncommon.-Examples:...
. Calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
-rich varieties often show steep pyramidal
Pyramid (geometry)
In geometry, a pyramid is a polyhedron formed by connecting a polygonal base and a point, called the apex. Each base edge and apex form a triangle. It is a conic solid with polygonal base....
forms. Crystals may be pseudo hexagonal due to equal development of different forms. Prism faces are striated horizontally. The mineral also occurs as columnar to fibrous, granular or rounded masses.
Optical properties
Strontianite is colourless, white, gray, light yellow, green or brown, colourless in transmitted light. It may be longitudinally zoned. It is transparent to translucent, with a vitreous (glassy) lustreLustre (mineralogy)
Lustre is a description of the way light interacts with the surface of a crystal, rock, or mineral. The word lustre traces its origins back to the Latin word lux, meaning "light", and generally implies radiance, gloss, or brilliance....
, resinous on broken surfaces, and a white streak
Streak (mineralogy)
The streak of a mineral is the color of the powder produced when it is dragged across an unweathered surface. Unlike the apparent color of a mineral, which for most minerals can vary considerably, the trail of finely ground powder generally has a more consistent characteristic color, and is thus...
.
It is a biaxial(-) mineral. The direction perpendicular to the plane containing the two optic axes
Optic axis of a crystal
The optic axis of a crystal is the direction in which a ray of transmitted light suffers no birefringence . Due to the internal structure of the crystal , light propagates along the optical axis differently than in other directions...
is called the optical direction Y. In strontianite Y is parallel to the b crystal axis. The optical direction Z lies in the plane containing the two optic axes and bisects the acute angle between them. In strontianite Z is parallel to the a crystal axis. The third direction X, perpendicular both to Y and to Z, is parallel to the c crystal axis. The refractive indices
Refractive index
In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....
are close to nα = 1.52, nβ = 1.66, nγ = 1.67, with different sources quoting slightly different values:
- nα = 1.520, nβ = 1.667, nγ = 1.669
- nα = 1.516 - 1.520, nβ = 1.664 - 1.667, nγ = 1.666 - 1.668
- nα = 1.517, nβ = 1.663, nγ = 1.667 (synthetic material)
The maximum birefringence
Birefringence
Birefringence, or double refraction, is the decomposition of a ray of light into two rays when it passes through certain anisotropic materials, such as crystals of calcite or boron nitride. The effect was first described by the Danish scientist Rasmus Bartholin in 1669, who saw it in calcite...
δ is 0.15 and the measured value of 2V
Conoscopic interference pattern
A conoscopic interference pattern or interference figure is a pattern of rings caused by optical interference observed when diverging light rays travel through a non isotropic substance. It is the best way to determine if a mineral is uniaxial or biaxial and also for determining optic sign in...
is 7°, calculated 12° to 8°.
If the colour of the incident light is changed, then the refractive indices are modified, and the value of 2V changes. This is known as dispersion of the optic axes. For strontianite the effect is weak, with 2V larger for violet light than for red light r < v.
Luminescence
Strontianite is almost always fluorescentFluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. It is a form of luminescence. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation...
. It fluoresces bright yellowish white under shortwave, mediumwave and longwave ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
radiation. If the luminescence persists after the ultraviolet source is switched off the sample is said to be phosphorescent
Phosphorescence
Phosphorescence is a specific type of photoluminescence related to fluorescence. Unlike fluorescence, a phosphorescent material does not immediately re-emit the radiation it absorbs. The slower time scales of the re-emission are associated with "forbidden" energy state transitions in quantum...
. Most strontianite phosphoresces a strong, medium duration, yellowish white after exposure to all three wavelengths. It is also fluorescent and phosphorescent in X-rays and electron beams
Cathode ray
Cathode rays are streams of electrons observed in vacuum tubes. If an evacuated glass tube is equipped with two electrodes and a voltage is applied, the glass opposite of the negative electrode is observed to glow, due to electrons emitted from and travelling perpendicular to the cathode Cathode...
. All materials will glow red hot if they are heated to a high enough temperature (provided they do not decompose first); some materials become luminescent at much lower temperatures, and this is known as thermoluminescence
Thermoluminescence
Thermoluminescence is a form of luminescence that is exhibited by certain crystalline materials, such as some minerals, when previously absorbed energy from electromagnetic radiation or other ionizing radiation is re-emitted as light upon heating of the material...
. Strontianite is sometimes thermoluminescent.
Physical properties
CleavageCleavage (crystal)
Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite crystallographic structural planes. These planes of relative weakness are a result of the regular locations of atoms and ions in the crystal, which create smooth repeating surfaces that are visible both in the...
is nearly perfect parallel to one set of prism faces, {110}
Miller index
Miller indices form a notation system in crystallography for planes and directions in crystal lattices.In particular, a family of lattice planes is determined by three integers h, k, and ℓ, the Miller indices. They are written , and each index denotes a plane orthogonal to a direction in the...
, and poor on {021}. Traces of cleavage have been observed on {010}.
Twinning
Crystal twinning
Crystal twinning occurs when two separate crystals share some of the same crystal lattice points in a symmetrical manner. The result is an intergrowth of two separate crystals in a variety of specific configurations. A twin boundary or composition surface separates the two crystals....
is very common, with twin plane {110}. The twins are usually contact twins; in a contact twin the two individuals appear to be reflections of each other in the twin plane. Penetration twins of strontainite are rarer; penetration twins are made up of interpenetrating individuals that are related to each other by rotation about a twin axis. Repeated twins are made up of three or more individuals twinned according to the same law. If all the twin planes are parallel then the twin is polysynthetic, otherwise it is cyclic. In strontianite repeated twinning forms cyclic twins with three or four individuals, or polysynthetic twins.
The mineral is brittle, and breaks with a subconchoidal to uneven fracture. It is quite soft, with a Mohs hardness of 3½, between calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
and fluorite
Fluorite
Fluorite is a halide mineral composed of calcium fluoride, CaF2. It is an isometric mineral with a cubic habit, though octahedral and more complex isometric forms are not uncommon...
. The specific gravity
Specific gravity
Specific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...
of the pure end member with no calcium substituting for strontium is 3.78, but most samples contain some calcium, which is lighter than strontium, giving a lower specific gravity, in the range 3.74 to 3.78. Substitutions of the heavier ions barium
Barium
Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Barium is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with...
and/or lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
increase the specific gravity, although such substitutions are never very abundant. Strontianite is soluble in dilute hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
HCl and it is not radioactive
Radioactive decay
Radioactive decay is the process by which an atomic nucleus of an unstable atom loses energy by emitting ionizing particles . The emission is spontaneous, in that the atom decays without any physical interaction with another particle from outside the atom...
.
Environment and associations
Strontianite is an uncommon low-temperature hydrothermal mineral formed in veinsVein (geology)
In geology, a vein is a distinct sheetlike body of crystallized minerals within a rock. Veins form when mineral constituents carried by an aqueous solution within the rock mass are deposited through precipitation...
in limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
, marl
Marl
Marl or marlstone is a calcium carbonate or lime-rich mud or mudstone which contains variable amounts of clays and aragonite. Marl was originally an old term loosely applied to a variety of materials, most of which occur as loose, earthy deposits consisting chiefly of an intimate mixture of clay...
, and chalk
Chalk
Chalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates shed from micro-organisms called coccolithophores....
, and in geodes and concretions. It occurs rarely in hydrothermal metallic veins but is common in carbonatite
Carbonatite
Carbonatites are intrusive or extrusive igneous rocks defined by mineralogic composition consisting of greater than 50 percent carbonate minerals. Carbonatites may be confused with marble, and may require geochemical verification....
s. It most likely crystallises at or near 100 °C. Its occurrence in open vugs
Vug
Vugs are small to medium-sized cavities inside rock that may be formed through a variety of processes. Most commonly cracks and fissures opened by tectonic activity are partially filled by quartz, calcite, and other secondary minerals. Open spaces within ancient collapse breccias are another...
and veins suggests crystallisation at very low pressures, probably at most equal to the hydrostatic pressure of the ground water. Under appropriate conditions it alters to celestine
Celestine
Celestine may refer to:Popes of the Roman Catholic Church:* Pope Celestine I * Pope Celestine II * Pope Celestine III * Pope Celestine IV * Pope Celestine V *Antipope Celestine II Other...
SrSO4, and it is itself found as an alteration from celestine. These two minerals are often found in association, together with baryte, calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
, harmotome
Harmotome
Harmotome is a mineral, one of the rarer zeolites; a hydrated barium silicate with formula: 5Al5,Si11O32·12. It forms vitreous white well defined monoclinic crystals, often associated with calcite and other zeolites...
and sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
.
Occurrences
Type locality
The type localityType locality (geology)
Type locality , also called type area or type locale, is the where a particular rock type, stratigraphic unit, fossil or mineral species is first identified....
is Strontian
Strontian
Strontian is the main village in Sunart, an area in western Lochaber, Highland, Scotland, on the A861 road. It lies on the north shore of Loch Sunart, close to the head of the loch...
, North West Highlands (Argyllshire), Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
, UK. The type material occurred in veins in gneiss
Gneiss
Gneiss is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from pre-existing formations that were originally either igneous or sedimentary rocks.-Etymology:...
.
Other UK localities include Brownley Hill Mine (Bloomsberry Horse Level), Nenthead, Alston Moor
Alston Moor
Alston Moor is an area of moorland and civil parish in Cumbria, England, based around the small town of Alston. The parish had a population of 2,156 at the 2001 census. As well as the town of Alston, the parish includes the villages of Garrigill and Nenthead, along with the hamlets of Nenthall,...
District, North Pennines, North and Western Region (Cumberland), Cumbria, England, associated with a suite of primary mierals (bournonite
Bournonite
Bournonite is a sulfosalt mineral species, a sulfantimonite of lead and copper with the formula PbCuSbS3.It was first mentioned by Philip Rashleigh in 1797 as an ore of antimony and was more completely described in 1804 by French crystallographer and mineralogist Jacques Louis de Bournon , after...
, millerite
Millerite
Millerite is a nickel sulfide mineral, NiS. It is brassy in colour and has an acicular habit, often forming radiating masses and furry aggregates...
and ullmannite
Ullmannite
Ullmannite is a nickel antimony sulfide mineral with formula: NiSbS. Considerable substitution occurs with cobalt and iron in the nickel site along with bismuth and arsenic in the antimony site...
) which are not common in other Mississippi Valley-type deposits
Carbonate hosted lead zinc ore deposits
Carbonate-hosted lead-zinc ore deposits are important and highly valuable concentrations of lead and zinc sulfide ores hosted within carbonate formations and which share a common genetic origin....
.
Canada
The Francon quarry, MontréalMontreal
Montreal is a city in Canada. It is the largest city in the province of Quebec, the second-largest city in Canada and the seventh largest in North America...
, Québec.
Strontianite is very common at the Francon Quarry, in a great variety of habits. It is a late stage mineral, sometimes found as multiple generations. It is found as translucent to opaque, white to pale yellow or beige generally smooth surfaced spheroids, hemispheres and compact spherical and botryoidal aggregates to 10 cm in diameter, and as spheres consisting of numerous radiating acicular crystals, up to 1 cm across. Also as tufts, parallel bundles, and sheaf-like clusters of fibrous to acicular crystals, and as white, finely granular porcelaneous and waxy globular aggregates. Transparent, pale pink, columnar to tabular sixling twins up to 1 cm in diameter have been found, and aggregates of stacked stellate sixling twins consisting of transparent, pale yellow tabular crystals.
Another Canadian occurrence is at Nepean
Nepean
-People:* Augustus Nepean , Middlesex county cricketer* Charles Nepean , Middlesex county cricketer and Oxford University footballer* Evan Nepean , British politician and colonial administrator...
, Ontario, in vein deposits in limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
.
Germany
Commercially important deposits occur in marls in WestphaliaWestphalia
Westphalia is a region in Germany, centred on the cities of Arnsberg, Bielefeld, Dortmund, Minden and Münster.Westphalia is roughly the region between the rivers Rhine and Weser, located north and south of the Ruhr River. No exact definition of borders can be given, because the name "Westphalia"...
, and it is also found with zeolites at Oberschaffhausen, Bötzingen
Bötzingen
Bötzingen is a municipality in the Breisgau-Hochschwarzwald district, Baden-Württemberg, Germany....
, Kaiserstuhl, Baden-Württemberg.
India
In Trichy (Tiruchirappalli; Tiruchi), Tiruchirapalli District, Tamil Nadu, it occurs with celestineCelestine
Celestine may refer to:Popes of the Roman Catholic Church:* Pope Celestine I * Pope Celestine II * Pope Celestine III * Pope Celestine IV * Pope Celestine V *Antipope Celestine II Other...
SrSO4, gypsum
Gypsum
Gypsum is a very soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. It is found in alabaster, a decorative stone used in Ancient Egypt. It is the second softest mineral on the Mohs Hardness Scale...
and phosphatic nodules in clay
Clay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
.
Mexico
It occurs in the Sierra MojadaSierra Mojada
Sierra Mojada is a city and seat of the municipality of Sierra Mojada, in the north-eastern Mexican state of Coahuila....
District, with celestine
Celestine
Celestine may refer to:Popes of the Roman Catholic Church:* Pope Celestine I * Pope Celestine II * Pope Celestine III * Pope Celestine IV * Pope Celestine V *Antipope Celestine II Other...
in a lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
-silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
deposit.
Russia
It occurs in the Kirovskii apatiteApatite
Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite, chlorapatite and bromapatite, named for high concentrations of OH−, F−, Cl− or Br− ions, respectively, in the crystal...
mine (Kirovsky Mine; Kirovskii Mine; Kirov Mine), Kukisvumchorr Mt, Khibiny Massif
Khibiny Massif
The Khibiny Massif, Khibiny Mountains, Khibinsky Mountains or Khibins, Khibinsky tundras, Khibiny is one of the two main mountain ranges of the Kola Peninsula, Russia, within the Arctic Circle, located between Imandra and Umbozero lakes.The massif is of oval shape of about 1,300 sq.km...
, Kola Peninsula
Kola Peninsula
The Kola Peninsula is a peninsula in the far northwest of Russia. Constituting the bulk of the territory of Murmansk Oblast, it lies almost completely to the north of the Arctic Circle and is washed by the Barents Sea in the north and the White Sea in the east and southeast...
, Murmanskaja Oblast', Northern Region, in late hydrothermal assemblages in cavities in pegmatites, associated with kukharenkoite-(La), microcline
Microcline
Microcline is an important igneous rock-forming tectosilicate mineral. It is a potassium-rich alkali feldspar. Microcline typically contains minor amounts of sodium. It is common in granite and pegmatites. Microcline forms during slow cooling of orthoclase; it is more stable at lower temperatures...
, albite
Albite
Albite is a plagioclase feldspar mineral. It is the sodium endmember of the plagioclase solid solution series. As such it represents a plagioclase with less than 10% anorthite content. The pure albite endmember has the formula NaAlSi3O8. It is a tectosilicate. Its color is usually pure white, hence...
, calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
, nenadkevichite
Nenadkevichite
Nenadkevichite is a rare silicate mineral containing niobium with formula: Si2O7·2H2O. It forms brown to yellow to rose colored orthorhombic dipyramidal crystals with a dull to earthy luster. It has a Mohs hardness of 5 and a specific gravity of 2.86.It was first reported in 1955 from a...
, hilairite, catapleiite, donnayite-(Y)
Donnayite-(Y)
Donnayite- is a rare earth carbonate consisting of the rare earth metal yttrium. It was first discovered in 1978 at Mont St-Hilaire, Quebec. Donnayite was subsequently identified and named after Joseph D.H. Donnay and his wife, Gabrielle Donnay. Both were prominent mineralogists and...
, synchysite-(Ce), pyrite
Pyrite
The mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold...
and others.
It also occurs at Yukspor Mountain, Khibiny Massif, Kola Peninsula, Murmanskaja Oblast', Northern Region, in an aegerine-natrolite
Natrolite
Natrolite is a tectosilicate mineral species belonging to the zeolite group. It is a hydrated sodium and aluminium silicate with the formula . The type locality is Hohentwiel, Hegau, Germany....
-microcline
Microcline
Microcline is an important igneous rock-forming tectosilicate mineral. It is a potassium-rich alkali feldspar. Microcline typically contains minor amounts of sodium. It is common in granite and pegmatites. Microcline forms during slow cooling of orthoclase; it is more stable at lower temperatures...
vein in foyaite, associated with aegirine
Aegirine
Aegirine is a member of the clinopyroxene group of inosilicates. Aegirine is the sodium endmember of the aegirine-augite series. Aegirine has the chemical formula NaFeSi2O6 in which the iron is present as Fe3+. In the aegirine-augite series the sodium is variably replaced by calcium with iron and...
, anatase
Anatase
Anatase is one of the three mineral forms of titanium dioxide, the other two being brookite and rutile. It is always found as small, isolated and sharply developed crystals, and like rutile, a more commonly occurring modification of titanium dioxide, it crystallizes in the tetragonal system; but,...
, ancylite-(Ce), barylite, catapleiite, cerite-(Ce), cerite-(La), chabazite-(Ca), edingtonite
Edingtonite
Edingtonite is a white, gray, brown, colorless, pink or yellow zeolite mineral. Its chemical formula is BaAl2Si3O10·4H2O. It has varieties with tetragonal, orthorhombic or triclinic crystals. It was named for Scottish mineral collector James Edington .-References and external links:* from...
, fluorapatite
Fluorapatite
Fluorapatite, often with the alternate spelling of fluoroapatite, is a mineral with the formula Ca53F . Fluorapatite is a hard crystalline solid. Although samples can have various color , the pure mineral is colorless as expected for a material lacking transition metals...
, galena
Galena
Galena is the natural mineral form of lead sulfide. It is the most important lead ore mineral.Galena is one of the most abundant and widely distributed sulfide minerals. It crystallizes in the cubic crystal system often showing octahedral forms...
, ilmenite
Ilmenite
Ilmenite is a weakly magnetic titanium-iron oxide mineral which is iron-black or steel-gray. It is a crystalline iron titanium oxide . It crystallizes in the trigonal system, and it has the same crystal structure as corundum and hematite....
, microcline
Microcline
Microcline is an important igneous rock-forming tectosilicate mineral. It is a potassium-rich alkali feldspar. Microcline typically contains minor amounts of sodium. It is common in granite and pegmatites. Microcline forms during slow cooling of orthoclase; it is more stable at lower temperatures...
, natrolite
Natrolite
Natrolite is a tectosilicate mineral species belonging to the zeolite group. It is a hydrated sodium and aluminium silicate with the formula . The type locality is Hohentwiel, Hegau, Germany....
, sphalerite
Sphalerite
Sphalerite is a mineral that is the chief ore of zinc. It consists largely of zinc sulfide in crystalline form but almost always contains variable iron. When iron content is high it is an opaque black variety, marmatite. It is usually found in association with galena, pyrite, and other sulfides...
and vanadinite
Vanadinite
Vanadinite is a mineral belonging to the apatite group of phosphates, with the chemical formula Pb53Cl. It is one of the main industrial ores of the metal vanadium and a minor source of lead. A dense, brittle mineral, it is usually found in the form of red hexagonal crystals. It is an uncommon...
. At the same locality it was found in alkaline pegmatite
Pegmatite
A pegmatite is a very crystalline, intrusive igneous rock composed of interlocking crystals usually larger than 2.5 cm in size; such rocks are referred to as pegmatitic....
veins associated with clinobarylite, natrolite
Natrolite
Natrolite is a tectosilicate mineral species belonging to the zeolite group. It is a hydrated sodium and aluminium silicate with the formula . The type locality is Hohentwiel, Hegau, Germany....
, aegirine
Aegirine
Aegirine is a member of the clinopyroxene group of inosilicates. Aegirine is the sodium endmember of the aegirine-augite series. Aegirine has the chemical formula NaFeSi2O6 in which the iron is present as Fe3+. In the aegirine-augite series the sodium is variably replaced by calcium with iron and...
, microcline
Microcline
Microcline is an important igneous rock-forming tectosilicate mineral. It is a potassium-rich alkali feldspar. Microcline typically contains minor amounts of sodium. It is common in granite and pegmatites. Microcline forms during slow cooling of orthoclase; it is more stable at lower temperatures...
, catapleiite, fluorapatite
Fluorapatite
Fluorapatite, often with the alternate spelling of fluoroapatite, is a mineral with the formula Ca53F . Fluorapatite is a hard crystalline solid. Although samples can have various color , the pure mineral is colorless as expected for a material lacking transition metals...
, titanite
Titanite
Titanite, or sphene , is a calcium titanium nesosilicate mineral, CaTiSiO5. Trace impurities of iron and aluminium are typically present...
, fluorite
Fluorite
Fluorite is a halide mineral composed of calcium fluoride, CaF2. It is an isometric mineral with a cubic habit, though octahedral and more complex isometric forms are not uncommon...
, galena
Galena
Galena is the natural mineral form of lead sulfide. It is the most important lead ore mineral.Galena is one of the most abundant and widely distributed sulfide minerals. It crystallizes in the cubic crystal system often showing octahedral forms...
, sphalerite
Sphalerite
Sphalerite is a mineral that is the chief ore of zinc. It consists largely of zinc sulfide in crystalline form but almost always contains variable iron. When iron content is high it is an opaque black variety, marmatite. It is usually found in association with galena, pyrite, and other sulfides...
, annite
Annite
Annite is a phyllosilicate mineral in the mica family. It has a chemical formula of KFe32+AlSi3O102. Annite is the iron end member of the biotite mica group, the iron rich analogue of magnesium rich phlogopite. Annite is monoclinic and contains tabular crystals and cleavage fragments with...
, astrophyllite
Astrophyllite
Astrophyllite is a very rare, brown to golden-yellow hydrous potassium iron titanium silicate mineral. Belonging to the astrophyllite group, astrophyllite may be classed either as an inosilicate, phyllosilicate, or an intermediate between the two. It forms an isomorphous series with kupletskite, to...
, lorenzenite
Lorenzenite
Lorenzenite is a rare sodium titanium silicate mineral with the formula Na2Ti2Si2O9 It is an orthorhombic mineral, variously found as colorless, grey, pinkish, or brown crystals.It was first identified in 1897 in rock samples from Narsarsuk, Greenland...
, labuntsovite-Mn, kuzmenkoite-Mn, cerite-(Ce), edingtonite
Edingtonite
Edingtonite is a white, gray, brown, colorless, pink or yellow zeolite mineral. Its chemical formula is BaAl2Si3O10·4H2O. It has varieties with tetragonal, orthorhombic or triclinic crystals. It was named for Scottish mineral collector James Edington .-References and external links:* from...
, ilmenite
Ilmenite
Ilmenite is a weakly magnetic titanium-iron oxide mineral which is iron-black or steel-gray. It is a crystalline iron titanium oxide . It crystallizes in the trigonal system, and it has the same crystal structure as corundum and hematite....
and calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
.
USA
In the Gulf coast of LouisianaLouisiana
Louisiana is a state located in the southern region of the United States of America. Its capital is Baton Rouge and largest city is New Orleans. Louisiana is the only state in the U.S. with political subdivisions termed parishes, which are local governments equivalent to counties...
and Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
, strontianite occurs with celestine
Celestine
Celestine may refer to:Popes of the Roman Catholic Church:* Pope Celestine I * Pope Celestine II * Pope Celestine III * Pope Celestine IV * Pope Celestine V *Antipope Celestine II Other...
in calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
cap rock of salt domes.
At the Minerva Number 1 Mine (Ozark-Mahoning Number 1 Mine) Ozark-Mahoning Group, Cave-in-Rock, Illinois
Cave-In-Rock, Illinois
Cave-In-Rock is a village in Hardin County, Illinois, United States. Its principal feature and attraction is a large nearby cave on the banks of the Ohio River. Cave-in-Rock was originally a stronghold for outlaws including; river pirates and highwaymen, Samuel Mason and James Ford, tavern...
, in the Kentucky Fluorspar District, Hardin County
Hardin County, Kentucky
As of the census of 2000, there were 94,174 people, 34,497 households, and 25,355 families residing in the county. The population density was . There were 37,673 housing units at an average density of...
strontanite occurs as white, brown or rarely pink tufts and bowties of acicular crystals with slightly curved terminations.
In the Silurian
Silurian
The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...
Lockport
Lockport
- Places :In Canada:* Lockport, Manitoba* Lockeport, Nova ScotiaIn the United States of America:* Lockport, Illinois* Lockport, Indiana* Lockport, Kentucky in Henry County, Kentucky* Lockport, Louisiana* Lockport , New York...
Group, Central and Western New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
strontianite is observed in cavities in eastern Lockport, where it occurs as small white radiating sprays of acicular crystals.
In Schoharie County, New York, it occurs in geodes and veins with celestine
Celestine
Celestine may refer to:Popes of the Roman Catholic Church:* Pope Celestine I * Pope Celestine II * Pope Celestine III * Pope Celestine IV * Pope Celestine V *Antipope Celestine II Other...
and calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
in limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
, and in Mifflin County, Pennsylvania, it occurs with aragonite
Aragonite
Aragonite is a carbonate mineral, one of the two common, naturally occurring, crystal forms of calcium carbonate, CaCO3...
, again in limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
.