Chalcophyllite
Encyclopedia
Chalcophyllite is a rare secondary copper
arsenate
mineral occurring in the oxidized zones of some arsenic
-bearing copper deposits. It was first described from material collected in Germany. At one time chalcophyllite from Wheal Tamar in Cornwall, England, was called tamarite, but this name is now discredited (not to be confused with the amphibole
mineral taramite, which is quite different). At Wheal Gorland
a specimen exhibiting partial replacement of liriconite, Cu2Al(AsO4)(OH)4.4(H2O), by chalcophyllite has been found. The mineral is named from the Greek, chalco "copper" and fyllon, "leaf", in allusion to its composition and platy structure. It is a classic Cornish
mineral that can be confused with tabular spangolite.
Cu18Al2(AsO4)3(SO4)3(OH)27·33(H2O) (molar mass 2956 g). The difference reflects the fact that the water content varies at room temperature based on relative humidity.
, 3 2/m with space group
R 3m or with space group R . Some authors choose a unit cell with three formula unit
s per cell (Z=3), and some a smaller unit cell with only 1.5 formula units per cell (Z=1.5). For the larger unit cell a = 10.77 Å, c = 57.5 Å, Z=3. For the smaller unit cell c is only half as long, a = 10.756 Å, c = 28.678 Å, Z = 1.5.
, and may be striated triangularly on these flattened faces. It may form rosettes, or be drusy, foliated or massive.
occurs with {1010} as the twin plane. Fracture is irregular. The mineral is soft, with hardness
only 2, the same as gypsum
. Specific gravity
is generally given in the range 2.67 to 2.69, but Webmineral has 2.4 to 2.66. Chalcophyllite is soluble in acids and in ammonia. It is not fluorescent, nor radioactive. The water content varies at room temperature based on relative humidity
. Chalcophyllite alters to chrysocolla
, which is a copper-aluminium silicate with the formula (Cu,Al)2H2Si2O5(OH)4·n(H2O).
and vitreous to subadamantine luster, pearly on {0001}. Crystals are transparent to translucent. It is uniaxial (-) with refractive indices nω = 1.618 to 1.632 and nε = 1.552 to 1.575. Indices of refraction vary markedly depending on the relative humidity since the water content varies at ambient temperature. It is pleochroic with O blue-green and E almost colorless.
-bearing hydrothermal copper deposits. Associated minerals include azurite
, malachite
, brochantite
, chrysocolla
, spangolite, connellite
, cuprite
, cyanotrichite
, strashimirite, parnauite, lavendulan
, cornubite
, langite
, clinoclase
, pharmacosiderite
and mansfieldite. The type material is conserved at the Mining Academy
, Freiberg, Germany. Notable occurrences include the Majuba Hill Mine, Antelope District
, Nevada, USA and Cornwall, including Wheal Gorland
, UK.
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...
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]....
mineral occurring in the oxidized zones 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 copper deposits. It was first described from material collected in Germany. At one time chalcophyllite from Wheal Tamar in Cornwall, England, was called tamarite, but this name is now discredited (not to be confused with the amphibole
Amphibole
Amphibole is the name of an important group of generally dark-colored rock-forming inosilicate minerals, composed of double chain tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures.-Mineralogy:...
mineral taramite, which is quite different). At Wheal Gorland
Wheal Gorland
Wheal Gorland was a metalliferous mine located just to the north-east of the village of St Day, Cornwall, in the United Kingdom. It was one of the most important Cornish mines of the late 18th and early 19th centuries, not only for the quantity of ore it produced, but also for the wide variety of...
a specimen exhibiting partial replacement of liriconite, Cu2Al(AsO4)(OH)4.4(H2O), by chalcophyllite has been found. The mineral is named from the Greek, chalco "copper" and fyllon, "leaf", in allusion to its composition and platy structure. It is a classic Cornish
Mining in Cornwall
Mining in Cornwall and Devon began in the early Bronze Age approximately 2,150 BC and ended with the South Crofty tin mine in Cornwall closing in 1998...
mineral that can be confused with tabular spangolite.
Formula
Two different formulae are quoted in the literature for chalcophyllite, Cu18Al2(AsO4)4(SO4)3(OH)24·36(H2O) (molar mass 3098 g) andCu18Al2(AsO4)3(SO4)3(OH)27·33(H2O) (molar mass 2956 g). The difference reflects the fact that the water content varies at room temperature based on relative humidity.
Unit cell
Chalcophyllite crystallizes in the trigonal crystal classCrystal system
In crystallography, the terms crystal system, crystal family, and lattice system each refer to one of several classes of space groups, lattices, point groups, or crystals...
, 3 2/m 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...
R 3m or with space group R . Some authors choose a unit cell with three formula unit
Formula unit
A formula unit in chemistry is the empirical formula of an ionic or covalent network solid compound used as an independent entity for stoichiometric calculations. It is the lowest whole number ratio of ions represented in an ionic compound...
s per cell (Z=3), and some a smaller unit cell with only 1.5 formula units per cell (Z=1.5). For the larger unit cell a = 10.77 Å, c = 57.5 Å, Z=3. For the smaller unit cell c is only half as long, a = 10.756 Å, c = 28.678 Å, Z = 1.5.
Crystal habit
Crystals are platy, six-sided and flattened perpendicular to the c crystal axisCrystal 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...
, and may be striated triangularly on these flattened faces. It may form rosettes, or be drusy, foliated or massive.
Physical properties
Cleavage is perfect perpendicular to the c crystal axis, and twinningCrystal 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....
occurs with {1010} as the twin plane. Fracture is irregular. The mineral is soft, with hardness
Mohs scale of mineral hardness
The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. It was created in 1812 by the German geologist and mineralogist Friedrich Mohs and is one of several definitions of hardness in...
only 2, the same as 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...
. 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...
is generally given in the range 2.67 to 2.69, but Webmineral has 2.4 to 2.66. Chalcophyllite is soluble in acids and in ammonia. It is not fluorescent, nor radioactive. The water content varies at room temperature based on relative humidity
Relative humidity
Relative humidity is a term used to describe the amount of water vapor in a mixture of air and water vapor. It is defined as the partial pressure of water vapor in the air-water mixture, given as a percentage of the saturated vapor pressure under those conditions...
. Chalcophyllite alters to chrysocolla
Chrysocolla
Chrysocolla is a hydrated copper silicate mineral with formula 2H2Si2O54·nH2O.-Properties:Chrysocolla has a blue-green color and is a minor ore of copper, having a hardness of 2.5 to 3.5.-Name and discovery:...
, which is a copper-aluminium silicate with the formula (Cu,Al)2H2Si2O5(OH)4·n(H2O).
Optical properties
Many copper minerals are blue or green in color; chalcophyllite is blue-green to emerald-green, with a pale 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 vitreous to subadamantine luster, pearly on {0001}. Crystals are transparent to translucent. It is uniaxial (-) with refractive indices nω = 1.618 to 1.632 and nε = 1.552 to 1.575. Indices of refraction vary markedly depending on the relative humidity since the water content varies at ambient temperature. It is pleochroic with O blue-green and E almost colorless.
Environment
Chalcophyllite is an uncommon secondary mineral occurring in the oxidized zones of some arsenicArsenic
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 hydrothermal copper deposits. 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...
, 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...
, brochantite
Brochantite
Brochantite is a sulfate mineral, one of a number of cupric sulfates. Its chemical formula is CuSO4·3Cu2. Formed in arid climates or in rapidly oxidizing copper sulfide deposits, it is named for its discoverer, the French geologist and mineralogist, A. J. M...
, chrysocolla
Chrysocolla
Chrysocolla is a hydrated copper silicate mineral with formula 2H2Si2O54·nH2O.-Properties:Chrysocolla has a blue-green color and is a minor ore of copper, having a hardness of 2.5 to 3.5.-Name and discovery:...
, spangolite, connellite
Connellite
Connellite is a very rare mineral species, a hydrous copper chloro-sulfate, Cu19[32|SO4|Cl4]·3H2O, crystallizing in the hexagonal system. It occurs as tufts of very delicate acicular crystals of a fine blue color, and is associated with other copper minerals of secondary origin, such as cuprite and...
, cuprite
Cuprite
Cuprite is an oxide mineral composed of copper oxide Cu2O, and is a minor ore of copper.Its dark crystals with red internal reflections are in the isometric system hexoctahedral class, appearing as cubic, octahedral, or dodecahedral forms, or in combinations. Penetration twins frequently occur...
, cyanotrichite
Cyanotrichite
Cyanotrichite is a copper aluminium sulfate mineral, Cu4Al2[12|SO4]·2H2O, also known as lettsomite, very similar to halotrichite, and a member of the same group. However, it is much rarer. It forms velvety aggregates of extremely fine fibres and radial aggregates...
, strashimirite, parnauite, lavendulan
Lavendulan
Lavendulan is an uncommon copper arsenate mineral, known for its characteristic intense electric blue color. It belongs to the lavendulan group, which has four members:* Lavendulan NaCaCu54Cl.5H2O* Lemanskiite NaCaCu54Cl.5H2O...
, cornubite
Cornubite
Cornubite is a rare secondary copper arsenate mineral with formula: Cu524. It was first described for its discovery in 1958 in Wheal Carpenter, Gwinear, Cornwall, England, UK. The name is from Cornubia, the medieval Latin name for Cornwall...
, langite
Langite
Langite is a rare hydrated copper sulfate mineral, with hydroxyl, found almost exclusively in druses of small crystals. It is formed from the oxidation of copper sulfides, and was first described in specimens from Cornwall, England. It is dimorphous with wroewolfeite...
, clinoclase
Clinoclase
Clinoclase is a hydrous copper arsenate mineral, Cu3AsO43. Clinoclase is a rare secondary copper mineral and forms acicular crystals in the fractured weathered zone above copper sulfide deposits. It occurs in vitreous, translucent dark blue to dark greenish blue colored crystals and botryoidal...
, pharmacosiderite
Pharmacosiderite
Pharmacosiderite is a hydrated basic ferric arsenate, with chemical formula KFe434·H2O and a molecular weight of 873.38 g/mol. It consists of the elements arsenic, iron, hydrogen, potassium, sodium and oxygen. It has a Mohs hardness of 2 to 3, about that of a finger nail...
and mansfieldite. The type material is conserved at the Mining Academy
Technische Universität Bergakademie Freiberg
The Technische Universität Bergakademie Freiberg is a small German University of Technology with about 5000 students in the city of Freiberg, Saxony...
, Freiberg, Germany. Notable occurrences include the Majuba Hill Mine, Antelope District
Antelope Range (Pershing County)
The Antelope Range is a mountain range in Pershing County, Nevada....
, Nevada, USA and Cornwall, including Wheal Gorland
Wheal Gorland
Wheal Gorland was a metalliferous mine located just to the north-east of the village of St Day, Cornwall, in the United Kingdom. It was one of the most important Cornish mines of the late 18th and early 19th centuries, not only for the quantity of ore it produced, but also for the wide variety of...
, UK.