sulfate mineral
The sulfate minerals are a class of minerals that include the sulfate ion () within their structure. The sulfate minerals occur commonly in primary evaporite depositional environments, as gangue minerals in hydrothermal veins and as secondary ...
with formula of K2Ca2Cu(SO4)4•2H2O.
Crystal class
Leightonite forms flattened to elongated bladed crystals of variously interpreted crystal structure. Its crystal system is reported as
triclinic
180px, Triclinic (a ≠ b ≠ c and α ≠ β ≠ γ )
In crystallography, the triclinic (or anorthic) crystal system is one of the 7 crystal systems. A crystal system is described by three basis vectors. In the triclinic system, the crystal is ...
morphologically, but also as pseudo-
orthorhombic
In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with ...
due to intricate lamellar twinning that mimics orthorhombic symmetry. Because it is triclinic, the crystal is represented by a system of three unequal vectors with corresponding unequal angles between them.
Optical class
Leightonite is
anisotropic
Anisotropy () is the property of a material which allows it to change or assume different properties in different directions, as opposed to isotropy. It can be defined as a difference, when measured along different axes, in a material's physic ...
, meaning it has more than one
refractive index
In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium.
The refractive index determines how much the path of light is bent, or ...
, in this case three as it is biaxial. The mineral can split polarized light into two rays with different direction and velocity, resulting in the appearance of interference colors when recombined and viewed under polarized light.
Discovery and occurrence
It was first described in 1938 for an occurrence in the
Chuquicamata Mine
Chuquicamata ( ; referred to as Chuqui for short) is the largest open pit copper mine in terms of excavated volume in the world. It is located in the north of Chile, just outside Calama, at above sea level. It is northeast of Antofagasta and ...
El Loa Province
El Loa Province ( es, Provincia El Loa) is one of three provinces of the northern Chilean region of Antofagasta (II). It is named after the longest of rivers in Chile, the Loa River. The provincial capital is Calama.
Geography and demography
Ac ...
,
Antofagasta Region
The Antofagasta Region ( es, Región de Antofagasta, ) is one of Chile's sixteen first-order administrative divisions. The second-largest region of Chile in area, it comprises three provinces, Antofagasta, El Loa and Tocopilla. It is bordered ...
,
Chile
Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...
,Mindat.org /ref> and named in honor of Tomas Leighton Donoso (1896–1967), Professor of Mineralogy at the University of Santiago, Chile.
It occurs in alkali oxidized zones of copper deposits and is associated with natrochalcite, blodite,
atacamite
Atacamite is a copper halide mineral: a copper(II) chloride hydroxide with formula Cu2Cl(OH)3. It was first described for deposits in the Atacama Desert of Chile in 1801 by D. de Fallizen. The Atacama Desert is also the namesake of the mineral.
...
kröhnkite
Kröhnkite ( Na2Cu(SO4)2•2H2O ) is a rare copper sulfate mineral named after B. Kröhnke who first researched it. Kröhnkite may be replaced by Saranchinaite, the anhydrous form of the mineral, if heated to temperatures above 200 °C (392&n ...
,
gypsum
Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywa ...
and
quartz
Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical fo ...
chalcanthite
Chalcanthite (, ) is a richly colored blue-green water-soluble sulfate mineral . It is commonly found in the late-stage oxidation zones of copper deposits. Due to its ready solubility, chalcanthite is more common in arid regions.
Chalcanthite i ...
,
anhydrite
Anhydrite, or anhydrous calcium sulfate, is a mineral with the chemical formula CaSO4. It is in the orthorhombic crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with the ...
and
lammerite
Copper arsenate (Cu3(AsO4)2·4H2O, or Cu5H2(AsO4)4·2H2O), also called copper orthoarsenate, tricopper arsenate, cupric arsenate, or tricopper orthoarsenate, is a blue or bluish-green powder insoluble in water and alcohol and soluble in aqueous ...
in
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Namibia
Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and ea ...
North Tyrol
North Tyrol, rarely North Tirol (german: Nordtirol), is the main part of the Austrian state of Tyrol, located in the western part of the country. The other part of the state is East Tyrol, which also belongs to Austria, but does not share a bord ...
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Austria
Austria, , bar, Östareich officially the Republic of Austria, is a country in the southern part of Central Europe, lying in the Eastern Alps. It is a federation of nine states, one of which is the capital, Vienna, the most populous c ...
Norway
Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and th ...
.
At the mining site of Chuquicamata, Chile, Leightonite is not found in rich ore; rather it only appears in borderland material within {{convert, 50, m, abbr=on of the surface, acting as a cement between rock fragments as it fills in cracks and cross-fiber veins in surfaces as a network of crystals. Although a hydrous sulfate of copper, it is not a major source of the element. Because of its rare nature, it is valued by mineral collectors.