Ophirite

Last updated
Ophirite
General
Category Tungstate
Formula
(repeating unit)
Ca2Mg4[Zn2Mn3+2(H2O)2(Fe3+W9O34)2] · 46•H2O
IMA symbol Oph [1]
Strunz classification 7.GB.80
Crystal system Triclinic
Crystal class 1 - Pinacoidal
Space group P1
Unit cell a = 11.9860(2)  Å, b = 13.2073(2) Å
c = 17.689(1) Å;
β= 85.364(6)°; α = 69.690(5)°; γ = 64.875(5)°; Z = 1
Identification
Formula mass 5726.57
ColorOrange-brown
Crystal habit Tablet-shaped crystals
Cleavage None observed
Fracture Irregular/uneven
Tenacity Brittle
Mohs scale hardness2
Luster Vitreous
Streak Pale orange
Diaphaneity Transparent
Specific gravity 4.060 g/cm3
Optical propertiesBiaxial positive
Refractive index nα= 1.730(3) nβ= 1.735(3) nγ= 1.770(3)
Birefringence δ = 0.040
Pleochroism Visible
Dispersion r > v, strong
Ultraviolet fluorescence None
References [2] [3]

Ophirite is a tungstate mineral first discovered in the Ophir Hill Consolidated mine at Ophir district, Oquirrh Mountains, Tooele County, Utah, United States of America. 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 Ca2Mg4[Zn2Mn3+2(H2O)2(Fe3+W9O34)2] · 46•H2O. 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. [2]

Contents

Occurrence

Ophirite is found in association with scheelite and pyrite. 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, galena, bournonite, unidentified sulfide minerals, foci of apatite, and sericite-containing pyrite, and is typically interface between scheelite and dolomite. Also present in the vein are crystals of sulfur and fluorite. [2]

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 {001} with irregular {100} and {110} bounding forms. Ophirite has no observed cleavage and irregular/uneven fracture. The measured specific gravity is 4.060 g/cm3. [3]

Optical properties

Ophirirte is biaxial positive, which means it will refract light along two axes. The mineral is optically biaxial positive, 2Vmeas. 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<Y<<Z. Observations indicate that chemical species are in their fully oxidized states. [2]

Chemical properties

Ophirite is a tungstate, and is the first mineral discovered containing [4]Fe3+[6]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[Zn2.02Mn3+1.82(H2O)2(Fe3+2.34W17.99O68)2] · 45.95•H2O. The ideal formula for ophirite is Ca2Mg4[Zn2Mn3+2(H2O)2(Fe3+W9O34)2] · 46•H2O. [2]

Chemical composition

Constituentwt%ideal wt%
CaO1.681.94
MgO2.792.78
ZnO2.862.81
Mn2O32.502.73
Fe2O33.252.76
Sb2O30.61-
WO371.9472.06
H2O15.2414.92
Total100.87100.00

[2]

X-ray crystallography

A Rigaku R-Axis Rapid II curved imaging plate microdiffractometer using monochromatized MoKα radiation was used to collect X-ray diffraction data for ophirite. [2] Ophirite is in the triclinic crystal system and in the space group P1. Its unit-cell dimensions were determined to be a = 11.9860(2)  Å; b = 13.2073(2) Å; c = 17.689(1) Å; β= 85.364(6)°; α = 69.690(5)°; γ = 64.875(5)°; Z = 1. [3]

See also

List of Minerals

Related Research Articles

<span class="mw-page-title-main">Mineral</span> Crystalline chemical element or compound formed by geologic processes

In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.

<span class="mw-page-title-main">Chalcopyrite</span> Copper iron sulfide mineral

Chalcopyrite ( KAL-kə-PY-ryte, -⁠koh-) is a copper iron sulfide mineral and the most abundant copper ore mineral. It has the chemical formula CuFeS2 and crystallizes in the tetragonal system. It has a brassy to golden yellow color and a hardness of 3.5 to 4 on the Mohs scale. Its streak is diagnostic as green-tinged black.

<span class="mw-page-title-main">Vivianite</span> Phosphate mineral

Vivianite (Fe2+
3
(PO
4
)
2
·8H
2
O
) is a hydrated iron phosphate mineral found in a number of geological environments. Small amounts of manganese Mn2+, magnesium Mg2+, and calcium Ca2+ may substitute for iron Fe2+ in the structure. Pure vivianite is colorless, but the mineral oxidizes very easily, changing the color, and it is usually found as deep blue to deep bluish green prismatic to flattened crystals.
Vivianite crystals are often found inside fossil shells, such as those of bivalves and gastropods, or attached to fossil bone.

<span class="mw-page-title-main">Marcasite</span> Iron disulfide (FeS2) with orthorhombic crystal structure

The mineral marcasite, sometimes called "white iron pyrite", is iron sulfide (FeS2) with orthorhombic crystal structure. It is physically and crystallographically distinct from pyrite, which is iron sulfide with cubic crystal structure. Both structures contain the disulfide S22− ion, having a short bonding distance between the sulfur atoms. The structures differ in how these di-anions are arranged around the Fe2+ cations. Marcasite is lighter and more brittle than pyrite. Specimens of marcasite often crumble and break up due to the unstable crystal structure.

<span class="mw-page-title-main">Powellite</span>

Powellite is a calcium molybdate mineral with formula CaMoO4. Powellite crystallizes with tetragonal – dipyramidal crystal structure as transparent adamantine blue, greenish-brown, yellow-to-grey typically anhedral forms. It exhibits distinct cleavage, and has a brittle-to-conchoidal fracture. It has a Mohs hardness of 3.5 to 4 and a specific gravity of 4.25. It forms a solid solution series with scheelite (calcium tungstate, CaWO4). It has refractive index values of nω=1.974 and nε=1.984.

<span class="mw-page-title-main">Warwickite</span>

Warwickite is an iron magnesium titanium borate mineral with the chemical formula (MgFe)3Ti(O, BO3)2orMg(Ti,Fe3+, Al)(BO3)O. It occurs as brown to black prismatic orthorhombic crystals which are vitreous and transparent. It has a Mohs hardness of 3 to 4 and a specific gravity of 3.36.

<span class="mw-page-title-main">Copiapite</span>

Copiapite is a hydrated iron sulfate mineral with formula: Fe2+Fe3+4(SO4)6(OH)2·20(H2O). Copiapite can also refer to a mineral group, the copiapite group.

<span class="mw-page-title-main">Sauconite</span> Trioctahedral (Zn2+) smectite, phyllosilicate mineral

Sauconite is a complex phyllosilicate mineral of the smectite clay group, formula Na0.3Zn3(SiAl)4O10(OH)2·4H2O. It forms soft earthy bluish white to red-brown monoclinic crystals typically massive to micaceous in habit. It has a Mohs hardness of 1 to 2 and a specific gravity of 2.45. Optically it is biaxial positive with refractive index values of nα = 1.550 - 1.580, nβ = 1.590 - 1.620 and nγ = 1.590 - 1.620. It is found in vugs and seams in the oxidized zones of zinc and copper deposits. It occurs in association with hemimorphite, smithsonite, chrysocolla, coronadite and various iron oxides.

<span class="mw-page-title-main">Plancheite</span>

Plancheite is a hydrated copper silicate mineral with the formula Cu8Si8O22(OH)4•(H2O). It is closely related to shattuckite in structure and appearance, and the two minerals are often confused.

<span class="mw-page-title-main">Zemannite</span>

Zemannite is a very rare oxide mineral with the chemical formula Mg0.5ZnFe3+[TeO3]3·4.5H2O. It crystallizes in the hexagonal crystal system and forms small prismatic brown crystals. Because of the rarity and small crystal size, zemannite has no applications and serves as a collector's item.

<span class="mw-page-title-main">Christite</span>

Christite is a mineral with the chemical formula TlHgAsS3. It is named after Dr. Charles L. Christ, a member of the U.S. Geological Survey. It usually comes in a crimson red or bright orange color. It has a density of 6.2 and has a rating between 1 and 2 on Mohs Hardness Scale. Christite has an adamantine luster and leaves behind an orange streak. Its crystal system is monoclinic with possible crystal classes of twofold symmetry, mirror plane symmetry, and twofold with a mirror plane. This means it can have radial symmetry, mirror plane symmetry, or mirror plane symmetry perpendicular to the two-fold axis. It is an anisotropic mineral, which means that it exhibits different properties when measured in different directions. In plane polarized light, its color is golden yellow. It is birefringent, which means that it has two distinct indices of refraction. This can be seen when one looks through the microscope with both polars crossed and sees the mineral change colors when it is rotated.

<span class="mw-page-title-main">Tsumcorite</span>

Tsumcorite is a rare hydrated lead arsenate mineral that was discovered in 1971, and reported by Geier, Kautz and Muller. It was named after the TSUMeb CORporation mine at Tsumeb, in Namibia, in recognition of the Corporation's support for mineralogical investigations of the orebody at its Mineral Research Laboratory.

<span class="mw-page-title-main">Ianbruceite</span>

Ianbruceite is a rare hydrated zinc arsenate with the formula [Zn2(OH)(H2O)(AsO4)](H2O)2; material from the Driggith mine has traces of cobalt. It was first discovered at Tsumeb, approved by the International Mineralogical Association as a new mineral species in 2011, reference IMA2011-49, and named for Ian Bruce, who founded "Crystal Classics" in the early 1990s, and was heavily involved in attempts to reopen the famous Tsumeb mine for specimen mining.
In 2013 new occurrences of ianbruceite were reported from the neighbouring Driggith and Potts Gill mines on High Pike in the Caldbeck Fells, Cumbria, England. Here the mineral is probably a post-mining product. Caldbeck Fells and Tsumeb are the only reported localities for ianbruceite to date (May 2013).

<span class="mw-page-title-main">Brianyoungite</span>

Brianyoungite is a secondary zinc carbonate mineral. The Commission on New Minerals, Nomenclature and Classification (CNMNC) of the International Mineralogical Association (IMA) classifies it as a carbonate with the formula Zn3(CO3)(OH)4, but sulfate groups SO4 also occupy the carbonate CO3 positions, in the ratio of about one sulfate to three carbonates, so other sources give the formula as Zn3(CO3,SO4)(OH)4, and Gaines et al. classify the mineral as a compound carbonate. It is similar in appearance to hydrozincite, another zinc carbonate. It was discovered in 1991 and designated IMA1991-053. In 1993 it was named "brianyoungite" after Brian Young (born 1947), a field geologist with the British Geological Survey, who provided the first specimens.

<span class="mw-page-title-main">Köttigite</span>

Köttigite is a rare hydrated zinc arsenate which was discovered in 1849 and named by James Dwight Dana in 1850 in honour of Otto Friedrich Köttig (1824–1892), a German chemist from Schneeberg, Saxony, who made the first chemical analysis of the mineral. It has the formula Zn3(AsO4)2·8H2O and it is a dimorph of metaköttigite, which means that the two minerals have the same formula, but a different structure: köttigite is monoclinic and metaköttigite is triclinic. There are several minerals with similar formulae but with other cations in place of the zinc. Iron forms parasymplesite Fe2+3(AsO4)2·8H2O; cobalt forms the distinctively coloured pinkish purple mineral erythrite Co3(AsO4)2·8H2O and nickel forms annabergite Ni3(AsO4)2·8H2O. Köttigite forms series with all three of these minerals and they are all members of the vivianite group.

<span class="mw-page-title-main">Carminite</span> Anhydrous arsenate mineral containing hydroxyl

Carminite (PbFe3+2(AsO4)2(OH)2) is an anhydrous arsenate mineral containing hydroxyl. It is a rare secondary mineral that is structurally related to palermoite (Li2SrAl4(PO4)4(OH)4). Sewardite (CaFe3+2(AsO4)2(OH)2) is an analogue of carminite, with calcium in sewardite in place of the lead in carminite. Mawbyite is a dimorph (same formula, different structure) of carminite; mawbyite is monoclinic and carminite is orthorhombic. It has a molar mass of 639.87 g. It was discovered in 1850 and named for the characteristic carmine colour.

<span class="mw-page-title-main">Talmessite</span>

Talmessite is a hydrated calcium magnesium arsenate, often with significant amounts of cobalt or nickel. It was named in 1960 for the type locality, the Talmessi mine, Anarak district, Iran. It forms a series with β-Roselite, where cobalt replaces some of the magnesium, and with gaitite, where zinc replaces the magnesium. All these minerals are members of the fairfieldite group. Talmessite is dimorphic with wendwilsonite.

<span class="mw-page-title-main">Rakovanite</span>

Rakovanite, (NH4)3Na3(V10O28) · 12H2O; formerly given as Na3(H3V10O28).15H2O; later, the ammonium ion was shown to be present and essential, is a member of the pascoite family. It is a transparent, brittle mineral occurring in the monoclinic crystal system. It is orange in color and has an orange-yellow colored streak. Rakovanite is soft with a Mohs hardness of 1 and a calculated density of 2.407g cm−3. It does not fluoresce in long- or short-wave ultraviolet radiation. Rakovanite crystals are up to one mm in maximum dimension and vary in habit from blocky to prismatic on [001], commonly exhibiting steps and striations parallel to [001]. Its name honors John Rakovan, former professor, Department of Geology and Environmental Earth Science, Miami University, State Mineralogist and Senior Museum Curator, New Mexico Bureau of Geology and Mineral Resources.

<span class="mw-page-title-main">Segnitite</span> Common iron oxide mineral

Segnitite is a lead iron(III) arsenate mineral. Segnitite was first found in the Broken Hill ore deposit in Broken Hill, New South Wales, Australia. In 1991, segnitite was approved as a new mineral. Segnitite has since been found worldwide near similar locality types where rocks are rich in zinc and lead especially. it was named for Australian mineralogist, gemologist and petrologist Edgar Ralph Segnit. The mineral was named after E. R. Segnit due to his contributions to Australian mineralogy.

Tuzlaite is a borate mineral, associated with halides, named after the Tuzla salt mines in Bosnia and Hercegovina. A multitude of rare evaporate minerals have been discovered there, it being the only major evaporate deposit in the Balkans. This mineral has been approved as tuzlaite by the International Commission on New Minerals and Mineral Names.

References

  1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi: 10.1180/mgm.2021.43 . S2CID   235729616.
  2. 1 2 3 4 5 6 7 Anthony R. Kampf, John M. Hughes, Barbara P. Nash, Stephen E. Wright, George R. Rossman, Joe Marty; Ophirite, Ca2Mg4[Zn2Mn23+(H2O)2(Fe3+W9O34)2]·46H2O, a new mineral with a heteropolytungstate tri-lacunary Keggin anion. American Mineralogist 2014;; 99 (5-6): 1045–1051. doi: https://doi.org/10.2138/am.2014.4699.
  3. 1 2 3 Hudson Institute of Mineralogy, 2014, Ophirite: https://www.mindat.org/min-43845.html (accessed November 2023)