Ophirite is a
tungstate
In chemistry, a tungstate is a compound that contains an oxyanion of tungsten or is a mixed oxide containing tungsten. The simplest tungstate ion is , "orthotungstate". Many other tungstates belong to a large group of polyatomic ions that are ter ...
mineral first discovered in the Ophir Hill Consolidated mine at Ophir district,
Oquirrh Mountains
The Oquirrh Mountains is a mountain range that runs north-south for approximately 30 miles (50 km) to form the west side of Utah's Salt Lake Valley, separating it from Tooele Valley. The range runs from northwestern Utah County–centr ...
, Tooele County, Utah,
United States of America
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territo ...
. It was found underground near a calcite cave in one veinlet, six centimeters wide by one meter long, surrounded by different sulfides. Before the closing of the mine in 1972, it was dominated by sulfide minerals, and the Ophir district was known for being a source of zinc, copper, silver, and lead ores. The crystals are formed as tablets. It is the first known mineral to contain a heteropolyanion, a lacunary defect derivative of the Keggin anion. The chemical formula of ophirite is Ca
2Mg
4 n2Mn3+2(H2O)2(Fe3+W9O34)2· 46•H
2O. The mineral has been approved by the Commission on New Minerals and Mineral Names, IMA, to be named ophirite for its type locality, the Ophir Consolidated mine.
Occurrence
Ophirite is found in association with
scheelite and
pyrite
The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Iron, FeSulfur, S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral.
Pyrite's metallic Luster (mineralogy), lust ...
. The production of the mineral is thought to be from oxidative alteration of sulfides: a reaction between dolomite and scheelite with oxidizing and late acidic hydrothermal solutions that are in the presence of calcium-rich and pyrite hornfels. It occurs in one veinlet, which is surrounded by
sphalerite
Sphalerite (sometimes spelled sphaelerite) is a sulfide mineral with the chemical formula . It is the most important ore of zinc. Sphalerite is found in a variety of deposit types, but it is primarily in Sedimentary exhalative deposits, sedimen ...
,
galena
Galena, also called lead glance, is the natural mineral form of lead(II) sulfide (PbS). It is the most important ore of lead and an important source of silver.
Galena is one of the most abundant and widely distributed sulfide minerals. It cryst ...
,
bournonite
Bournonite is a sulfosalt mineral species, trithioantimoniate 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 crystallo ...
, unidentified sulfide minerals, foci of
apatite
Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of OH−, F− and Cl− ions, respectively, in the crystal. The formula of the admixture of the three most common e ...
, and sericite-containing pyrite, and is typically interface between scheelite and dolomite. Also present in the vein are crystals of
sulfur
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
and
fluorite.
Physical properties
Ophirite is an orange-brown, transparent mineral with a vitreous luster. It exhibits a hardness of 2 on the
Mohs hardness scale. Ophirite occurs as tablet-shaped crystals on with irregular and bounding forms. Ophirite has no observed cleavage and irregular/uneven fracture. The measured specific gravity is 4.060 g/cm
3.
Optical properties
Ophirirte is
biaxial positive, which means it will refract light along two axes. The mineral is optically
biaxial positive, 2V
meas. 43(2)°. The refractive indices are: α ~ 1.730(3), β ~ 1.735(3), and γ ~ 1.770(3)°. Dispersion is strong, r > v. Its
pleochroism is light orange brown for X and Y, and orange brown for Z, where X
Chemical properties
Ophirite is a
tungstate
In chemistry, a tungstate is a compound that contains an oxyanion of tungsten or is a mixed oxide containing tungsten. The simplest tungstate ion is , "orthotungstate". Many other tungstates belong to a large group of polyatomic ions that are ter ...
, and is the first mineral discovered containing
/sup>Fe3+ /sup>W6+9O34, a group in the structural unit of the ophirite polyanion. Tri-lacunary Keggin anions are well known in synthetic compounds, but ophirite is the first known example of a mineral with a tri-lacunary Keggin polyanion.The empirical chemical formula for ophirite calculated on the basis of 30 cations, is Ca1.73Mg3.99 n2.02Mn3+1.82(H2O)2(Fe3+2.34W17.99O68)2· 45.95•H2O. The ideal formula for ophirite is Ca2Mg4 n2Mn3+2(H2O)2(Fe3+W9O34)2· 46•H2O.
Chemical composition
[
]
X-ray crystallography
A Rigaku R-Axis Rapid II curved imaging plate microdiffractometer using monochromatized Mo''K''α radiation was used to collect X-ray diffraction data for ophirite.
See also
List of Minerals
This is a list of minerals for which there are articles on Wikipedia.
Minerals are distinguished by various chemical and physical properties. Differences in chemical composition and crystal structure distinguish the various ''species''. Within a m ...
References
{{Authority control
Natural materials
Tungstate minerals
Triclinic minerals
Minerals in space group 1
Wikipedia Student Program
Zinc minerals
Manganese minerals