Tsumebite
Encyclopedia
Tsumebite is a rare phosphate mineral named in 1912 after the locality where it was first found, the Tsumeb mine in Namibia, well known to mineral collectors for the wide range of minerals found there. Tsumebite is a compound phosphate
and sulfate
of lead
and copper
, with hydroxyl
, formula Pb2Cu(PO4)(SO4)(OH). There is a similar mineral called arsentsumebite, where the phosphate
group PO4 is replaced by the arsenate
group AsO4, giving the formula Pb2Cu(AsO4)(SO4)(OH). Both minerals are members of the brackebuschite group.
, space group
P21/m. The group includes:
of large cations
. B and T represent different elements in different members of the group. Chains formed from the B octahedra link through the oxygen
s of TO4(2) tetrahedra, while the large cation polyhedra form double chains parallel to the b crystal axis
through edge sharing with TO4(1) tetrahedra. The result is a tight three-dimensional structure. In tsumebite copper
ions occupy the B sites, and phosphorus
and sulfur
occupy the T sites. Lead
is the large cation.
crystal class 2/m, meaning that it has one twofold axis of symmetry
perpendicular to a mirror plane
. The space group
is P 21/m, meaning that the crystal lattice is a primitive lattice
, with structural elements only at the vertices of the unit cell. These structural elements are made up of two formula units (Z = 2).
Unit cell
parameters are a = 8.69 Å, b = 5.78 Å, c = 7.86 Å, β = 111.87° or a = 8.70 Å, b = 5.80 Å, c = 7.85 Å, β = 111.5°.
and an adamantine (diamond-like) to vitreous (glassy) luster
. It is biaxial (+) with refractive indices
Nx = 1.885 to 1.900, Ny = 1.920 and Nz = 1.942 to 1.956. It is faintly pleochroic
with X = Y = very pale blue to colorless and Z = robin’s-egg-blue.
. Cleavage is absent, but twinning
is almost universal, and twins may be multiple, with serrated re-entrants. It is brittle, with an uneven fracture, hardness 3½ and specific gravity
6.13. It is readily soluble in hydrochloric acid
HCl and slowly soluble in nitric acid
HNO3. It is not radioactive
.
in the oxidised zone of some arsenic
-bearing lead-copper deposits, with other lead-bearing phosphates and sulfates. Associated minerals include azurite
, smithsonite
, malachite
, cerussite
, mimetite
, wulfenite
and olivenite
. The type locality is the Tsumeb mine, Tsumeb, Otjikoto Region, Namibia. The Handbook of Mineralogy states that the type material was destroyed by bombing, but does not indicate when or where.
Tsumebite occurs at Morenci, Arizona
, predominantly as twinned crystals associated with wulfenite
, olivenite
and the hyalite
variety of opal
. At Broken Hill, New South Wales
, Australia, tsumebite has been found as lustrous pale blue to bluish green crystals. It usually occurs with yellow crusts of corkite
-hinsdalite, colorless to white pyromorphite
needles and sprays of pale greyish green zinc
ian libethenite
. Less commonly found with scholzite and torbernite
.
Phosphate
A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...
and sulfate
Sulfate
In inorganic chemistry, a sulfate is a salt of sulfuric acid.-Chemical properties:...
of 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...
and 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 hydroxyl
Hydroxyl
A hydroxyl is a chemical group containing an oxygen atom covalently bonded with a hydrogen atom. In inorganic chemistry, the hydroxyl group is known as the hydroxide ion, and scientists and reference works generally use these different terms though they refer to the same chemical structure in...
, formula Pb2Cu(PO4)(SO4)(OH). There is a similar mineral called arsentsumebite, where the phosphate
Phosphate
A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...
group PO4 is replaced by the arsenate
Arsenate
The arsenate ion is AsO43−.An arsenate is any compound that contains this ion. Arsenates are salts or esters of arsenic acid.The arsenic atom in arsenate has a valency of 5 and is also known as pentavalent arsenic or As[V]....
group AsO4, giving the formula Pb2Cu(AsO4)(SO4)(OH). Both minerals are members of the brackebuschite group.
The brackebuschite group
The minerals in the brackebuschite group have the general formula A2B(H2O,OH)(TO4)2 and crystallise in the monoclinic systemMonoclinic crystal system
In crystallography, the monoclinic crystal system is one of the 7 lattice point groups. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal length, as in the orthorhombic system. They form a rectangular prism with a...
, 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...
P21/m. The group includes:
- brackebuschite Pb2Mn3+(VO4)2(OH)
- arsenbrackebuschite Pb2(Fe3+,Zn)(AsO4)2(OH,H2O)
- gamagarite Ba2Fe3+(VO4)2(OH)
- goedkenite Sr2Al(PO4)2(OH)
- bearthite Ca2Al(PO4)2OH
- tsumebite Pb2Cu(PO4)(SO4)(OH)
- arsentsumebite Pb2Cu(AsO4)(SO4)(OH)
- vauqueliniteVauqueliniteVauquelinite is a complex mineral with the formula CuPb2CrO4PO4OH making it a combined chromate and phosphate of copper and lead. Discovered in 1818 in the Beryozovskoye deposit, Urals, Russia, it is named after Louis Vauquelin , a French chemist....
Cu2+Pb2(CrO4)(PO4)(OH) - fornaciteFornaciteFornacite is a rare lead, copper chromate arsenate hydroxide mineral with formula: Pb2Cu. The phosphate ion is also reported as substituting in the mineral. It forms variably green to yellow, translucent to transparent crystals in the monoclinic - prismatic crystal system...
CuPb2(CrO4)(AsO4)(OH) - molybdofornacite CuPb2MoO4AsO4(OH)
Structure
The structure of the brackebuschite group minerals is composed of B-(O,OH)6 octahedra, two non-equivalent TO4 tetrahedra, TO4(1) and TO4(2), and two different irregular polyhedraPolyhedron
In elementary geometry a polyhedron is a geometric solid in three dimensions with flat faces and straight edges...
of large 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...
. B and T represent different elements in different members of the group. Chains formed from the B octahedra link through 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...
s of TO4(2) tetrahedra, while the large cation polyhedra form double chains parallel to the b crystal 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...
through edge sharing with TO4(1) tetrahedra. The result is a tight three-dimensional structure. In tsumebite 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...
ions occupy the B sites, and phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
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...
occupy the T sites. 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...
is the large cation.
Unit cell
Tsumebite belongs to the monoclinicMonoclinic crystal system
In crystallography, the monoclinic crystal system is one of the 7 lattice point groups. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal length, as in the orthorhombic system. They form a rectangular prism with a...
crystal class 2/m, meaning that it has one twofold axis of symmetry
Rotational symmetry
Generally speaking, an object with rotational symmetry is an object that looks the same after a certain amount of rotation. An object may have more than one rotational symmetry; for instance, if reflections or turning it over are not counted, the triskelion appearing on the Isle of Man's flag has...
perpendicular to a mirror plane
Reflection symmetry
Reflection symmetry, reflectional symmetry, line symmetry, mirror symmetry, mirror-image symmetry, or bilateral symmetry is symmetry with respect to reflection. That is, a figure which does not change upon undergoing a reflection has reflectional symmetry.In 2D there is a line of symmetry, in 3D a...
. 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 P 21/m, meaning that the crystal lattice is a primitive lattice
Wigner-Seitz cell
The Wigner–Seitz cell, named after Eugene Wigner and Frederick Seitz, is a type of Voronoi cell used in the study of crystalline material in solid-state physics....
, with structural elements only at the vertices of the unit cell. These structural elements are made up of two formula units (Z = 2).
Unit cell
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...
parameters are a = 8.69 Å, b = 5.78 Å, c = 7.86 Å, β = 111.87° or a = 8.70 Å, b = 5.80 Å, c = 7.85 Å, β = 111.5°.
Optical properties
Tsumebite is an emerald-green color, transparent and green in transmitted light, with a green streakStreak (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...
and an adamantine (diamond-like) to vitreous (glassy) luster
Lustre (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....
. It is biaxial (+) with 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....
Nx = 1.885 to 1.900, Ny = 1.920 and Nz = 1.942 to 1.956. It is faintly pleochroic
Pleochroism
Pleochroism is an optical phenomenon in which a substance appears to be different colors when observed at different angles with polarized light.- Background :Anisotropic crystals will have optical properties that vary with the direction of light...
with X = Y = very pale blue to colorless and Z = robin’s-egg-blue.
Physical properties
The mineral typically occurs as crusts of intergrown crystals on matrixMatrix (geology)
The matrix or groundmass of rock is the finer grained mass of material in which larger grains, crystals or clasts are embedded.The matrix of an igneous rock consists of finer grained, often microscopic, crystals in which larger crystals are embedded. This porphyritic texture is indicative of...
. Cleavage is absent, but 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 almost universal, and twins may be multiple, with serrated re-entrants. It is brittle, with an uneven fracture, hardness 3½ and 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...
6.13. It is readily soluble in 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 slowly soluble in nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
HNO3. 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
Tsumebite is a rare secondary mineralSupergene (geology)
In ore deposit geology, supergene processes or enrichment occur relatively near the surface. Supergene processes include the predominance of meteoric water circulation with concomitant oxidation and chemical weathering. The descending meteoric waters oxidize the primary sulfide ore minerals and...
in the oxidised zone of some arsenic
Arsenic
Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...
-bearing lead-copper deposits, with other lead-bearing phosphates and sulfates. Associated minerals include azurite
Azurite
Azurite is a soft, deep blue copper mineral produced by weathering of copper ore deposits. It is also known as Chessylite after the type locality at Chessy-les-Mines near Lyon, France...
, smithsonite
Smithsonite
Smithsonite, or zinc spar, is zinc carbonate , a mineral ore of zinc. Historically, smithsonite was identified with hemimorphite before it was realised that they were two distinct minerals. The two minerals are very similar in appearance and the term calamine has been used for both, leading to some...
, malachite
Malachite
Malachite is a copper carbonate mineral, with the formula Cu2CO32. This green-colored mineral crystallizes in the monoclinic crystal system, and most often forms botryoidal, fibrous, or stalagmitic masses. Individual crystals are rare but do occur as slender to acicular prisms...
, cerussite
Cerussite
Cerussite 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...
, mimetite
Mimetite
Mimetite, whose name derives from the Greek Μιμητής mimethes, meaning "imitator", is an arsenate mineral which forms as a secondary mineral in lead deposits, usually by the oxidation of galena and arsenopyrite. The name is a reference to mimetite's resemblance to the mineral pyromorphite...
, wulfenite
Wulfenite
Wulfenite is a lead molybdate mineral with the formula PbMoO4. It can be most often found as thin tabular crystals with a bright orange-red to yellow-orange color, sometimes brown, although the color can be highly variable. In its yellow form it is sometimes called "yellow lead ore".It crystallizes...
and olivenite
Olivenite
Olivenite is a copper arsenate mineral, formula Cu2AsO4OH. It crystallizes in the monoclinic system , and is sometimes found in small brilliant crystals of simple prismatic habit terminated by domal faces...
. The type locality is the Tsumeb mine, Tsumeb, Otjikoto Region, Namibia. The Handbook of Mineralogy states that the type material was destroyed by bombing, but does not indicate when or where.
Tsumebite occurs at Morenci, Arizona
Morenci, Arizona
Morenci is a census-designated place in Greenlee County, Arizona, United States. The population was 1,879 at the 2000 census. It is part of the Safford Micropolitan Statistical Area...
, predominantly as twinned crystals associated with wulfenite
Wulfenite
Wulfenite is a lead molybdate mineral with the formula PbMoO4. It can be most often found as thin tabular crystals with a bright orange-red to yellow-orange color, sometimes brown, although the color can be highly variable. In its yellow form it is sometimes called "yellow lead ore".It crystallizes...
, olivenite
Olivenite
Olivenite is a copper arsenate mineral, formula Cu2AsO4OH. It crystallizes in the monoclinic system , and is sometimes found in small brilliant crystals of simple prismatic habit terminated by domal faces...
and the hyalite
Hyalite
Hyalite is a form of opal with a glassy and clear appearance which exhibits an internal play of colors and has natural inclusions. It is also called Muller's glass, water opal and jalite. Its Mohs hardness is 5.5 to 6 and it has a specific gravity of 2.1. It is an amorphous form of silica . Its...
variety of opal
Opal
Opal is an amorphous form of silica related to quartz, a mineraloid form, not a mineral. 3% to 21% of the total weight is water, but the content is usually between 6% to 10%. It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock, being most...
. At Broken Hill, New South Wales
Broken Hill, New South Wales
-Geology:Broken Hill's massive orebody, which formed about 1,800 million years ago, has proved to be among the world's largest silver-lead-zinc mineral deposits. The orebody is shaped like a boomerang plunging into the earth at its ends and outcropping in the centre. The protruding tip of the...
, Australia, tsumebite has been found as lustrous pale blue to bluish green crystals. It usually occurs with yellow crusts of corkite
Corkite
Corkite is a phosphate mineral in the beudantite subgroup of the alunite group. Corkite is the phosphate analogue of beudantite and with it, a complete solid solution range exists. Corkite will also form a solid solution with kintoreite....
-hinsdalite, colorless to white pyromorphite
Pyromorphite
Pyromorphite is a mineral species composed of lead chlorophosphate: Pb53Cl, sometimes occurring in sufficient abundance to be mined as an ore of lead. Crystals are common, and have the form of a hexagonal prism terminated by the basal planes, sometimes combined with narrow faces of a hexagonal...
needles and sprays of pale greyish green zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
ian libethenite
Libethenite
Libethenite is a rare copper phosphate hydroxide mineral. It forms striking, dark green orthorhombic crystals. It was discovered in 1823 in Ľubietová, Slovakia and is named after the German name of that locality .-References:...
. Less commonly found with scholzite and torbernite
Torbernite
The chemical formula of torbenite is similar to that of autunite in which a Cu2+ cation replaces a Ca2+. The number of water hydration molecules can vary between 12 and 8, giving rise to the variety of metatorbernite when torbernite spontaneously dehydrates...
.
External links
- Jmol: http://rruff.geo.arizona.edu/AMS/viewJmol.php?id=14449