Mimetite

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Mimetite
Mimetite - Congreso-Leon mines, San Pedro Corralitos, Chihuahua, Mexico.jpg
Golden yellow botryoidal mimetite from Congreso-León mines, Mexico
General
Category Arsenate minerals
Apatite group
Formula
(repeating unit)
Pb5(AsO4)3Cl
IMA symbol Mim [1]
Strunz classification 8.BN.05
Crystal system Hexagonal
Crystal class Dipyramidal (6/m)
(same H-M symbol)
Space group P63/m
Unit cell a = 10.250(2) Å,
c = 7.454(1) Å; Z = 2
Identification
ColorPale to bright yellow, yellowish brown, yellow-orange, white, may be colorless
Crystal habit Prismatic to acicular crystals; reniform, botryoidal, globular,
Twinning Rare on {1122}
Cleavage [1011] Imperfect
Fracture Brittle, conchoidal
Tenacity Brittle
Mohs scale hardness3.5–4
Luster Resinous, subadamantine
Streak White
Diaphaneity Transparent to translucent
Specific gravity 7.1–7.24
Optical propertiesUniaxial (−), anomalously biaxial
Refractive index nω = 2.147 nε = 2.128
Birefringence 0.019
Pleochroism Weak
References [2] [3] [4]

Mimetite is a lead arsenate chloride mineral ( Pb 5(As O 4)3 Cl ) which forms as a secondary mineral in lead deposits, usually by the oxidation of galena and arsenopyrite. The name derives from the Greek Μιμητής mimetes, meaning "imitator" and refers to mimetite's resemblance to the mineral pyromorphite. This resemblance is not coincidental, as mimetite forms a mineral series with pyromorphite (Pb5(PO4)3Cl) and with vanadinite (Pb5(VO4)3Cl). Notable occurrences are Mapimi, Durango, Mexico and Tsumeb, Namibia.

Contents

Properties

Mimetite from Namibia Mimetite 21207.jpg
Mimetite from Namibia

Mimetite is a lead chloride arsenate mineral with the composition Pb5(AsO4)3Cl. It is a secondary mineral, formed by oxidation of primary lead minerals in arsenic-bearing lead deposits. [2] It typically forms short hexagonal crystals that are yellow to brown to orange in color, very brittle, moderately hard (Mohs hardness 3.5–4), and dense (specific gravity 7.24). It is distinctive for its lack of transparency, its resinous to adamantine luster, and its solubility in nitric acid. [5]

Mimetite forms a complete solid solution series with pyromorphite, with phosphate ( P O 3−
4
) substituting for arsenate ( As O 3−
4
). The two minerals are almost identical in their properties and can be difficult to distinguish except by laboratory tests. Pyromorphite is the more common mineral at most locales. [5]

Campylite is a name applied to mimetite or pyromorphite that crystallizes as distinctive barrel-shaped crystals forming curved hemispherical aggregates. [5] Bellite is a name formerly applied to a chromium-bearing mimetite, or possibly a mixture of crocoite, mimetite and quartz, which forms attractive orange red crystals, but has been discredited as a distinct mineral species. [6]

Occurrences

Mimetite is found in association with lead and arsenic minerals, including pyromorphite, cerussite, hemimorphite, smithsonite, vanadinite, anglesite, pyrite, mottramite, willemite, and wulfenite. [5] [2] Good specimens have been reported from Gila County, Arizona, US; Ojocaliente, Zacatecas, Mexico; Cumberland, England; Johanngeorgenstadt, Saxony, Germany; Namibia; and Broken Hill, Australia. [5]

Related Research Articles

<span class="mw-page-title-main">Vanadinite</span> Apatite supergroup, vanadate mineral

Vanadinite is a mineral belonging to the apatite group of phosphates, with the chemical formula Pb5(VO4)3Cl. It is one of the main industrial ores of the metal vanadium and a minor source of lead. A dense, brittle mineral, it is usually found in the form of red hexagonal crystals. It is an uncommon mineral, formed by the oxidation of lead ore deposits such as galena. First discovered in 1801 in Mexico, vanadinite deposits have since been unearthed in South America, Europe, Africa, and North America.

<span class="mw-page-title-main">Wulfenite</span> Molybdate mineral

Wulfenite is a lead molybdate mineral with the formula PbMoO4. It often occurs 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".

<span class="mw-page-title-main">Pyromorphite</span> Lead chlorophosphate mineral

Pyromorphite is a mineral species composed of lead chlorophosphate: Pb5(PO4)3Cl, 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 pyramid. Crystals with a barrel-like curvature are not uncommon. Globular and reniform masses are also found. Pyromorphite is part of the apatite group of minerals and bears a close resemblance physically and chemically with two other minerals: mimetite (Pb5(AsO4)3Cl) and vanadinite (Pb5(VO4)3Cl). The resemblance in external characters is so close that, as a rule, it is only possible to distinguish between them by chemical tests. They were formerly confused under the names green lead ore and brown lead ore (German: Grünbleierz and Braunbleierz).

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

Descloizite is a rare mineral species consisting of basic lead and zinc vanadate, (Pb, Zn)2(OH)VO4, crystallizing in the orthorhombic crystal system and isomorphous with olivenite. Appreciable gallium and germanium may also be incorporated into the crystal structure.

<span class="mw-page-title-main">Vauquelinite</span> Complex mineral

Vauquelinite is a complex mineral with the formula CuPb2(CrO4)(PO4)(OH) making it a combined chromate and phosphate of copper and lead. It forms a series with the arsenate mineral fornacite.

<span class="mw-page-title-main">Legrandite</span> Rare zinc arsenate mineral

Legrandite is a rare zinc arsenate mineral, Zn2(AsO4)(OH)·(H2O).

<span class="mw-page-title-main">Duftite</span> Arsenate mineral

Duftite is a relatively common arsenate mineral with the formula CuPb(AsO4)(OH), related to conichalcite. It is green and often forms botryoidal aggregates. It is a member of the adelite-descloizite Group, Conichalcite-Duftite Series. Duftite and conichalcite specimens from Tsumeb are commonly zoned in color and composition. Microprobe analyses and X-ray powder-diffraction studies indicate extensive substitution of Zn for Cu, and Ca for Pb in the duftite structure. This indicates a solid solution among conichalcite, CaCu(AsO4 )(OH), austinite, CaZn(AsO4)(OH) and duftite PbCu(AsO4)(OH), all of them belonging to the adelite group of arsenates. It was named after Mining Councilor G Duft, Director of the Otavi Mine and Railroad Company, Tsumeb, Namibia. The type locality is the Tsumeb Mine, Tsumeb, Otjikoto Region, Namibia.

<span class="mw-page-title-main">Conichalcite</span> Arsenate mineral

Conichalcite, CaCu(AsO4)(OH), is a relatively common arsenate mineral related to duftite (PbCu(AsO4)(OH)). It is green, often botryoidal, and occurs in the oxidation zone of some metal deposits. It occurs with limonite, malachite, beudantite, adamite, cuproadamite, olivenite and smithsonite.

<span class="mw-page-title-main">Plumbogummite</span> Alunite supergroup, phosphate mineral

Plumbogummite is a rare secondary lead phosphate mineral, belonging to the alunite supergroup of minerals, crandallite subgroup. Some other members of this subgroup are:

<span class="mw-page-title-main">Picropharmacolite</span> Rare arsenate mineral

Picropharmacolite, Ca4Mg(AsO3OH)2(AsO4)2·11H2O, is a rare arsenate mineral. It was named in 1819 from the Greek for bitter, in allusion to its magnesium content, and its chemical similarity to pharmacolite. The mineral irhtemite, Ca4Mg(AsO3OH)2(AsO4)2·4H2O, has the same composition as picropharmacolite, except that it has only four water molecules per formula unit, instead of eleven. It may be formed by the dehydration of picropharmacolite.

<span class="mw-page-title-main">Tsumebite</span> Rare phosphate mineral

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.

<span class="mw-page-title-main">Minium (mineral)</span>

Minium is the naturally occurring form of lead tetroxide, Pb2+2Pb4+O4 also known as red lead. Minium is a light-to-vivid red and may have brown-to-yellow tints. It typically occurs in scaly-to-earthy masses. It crystallizes in the tetragonal crystal system.

<span class="mw-page-title-main">Warikahnite</span> Rare zinc arsenate mineral

Warikahnite is a rare zinc arsenate mineral of the triclinic crystal system with Hermann-Mauguin notation 1, belonging to the space group P1. It occurs in the Tsumeb mine in Namibia on corroded tennantite in the second oxidation zone under hydrothermal conditions in a dolomite-hosted polymetallic ore deposit. It is associated with adamite, stranskiite, koritnigite, claudetite, tsumcorite, and ludlockite. The origin of discovery was in a dolomite ore formation within an oxidized hydrothermal zone, in the E9 pillar, 31st level of the Tsumeb Mine in Namibia, Southwest Africa. It has also been found at Lavrion, Greece and Plaka, Greece as microscopic white needles.

<span class="mw-page-title-main">Tsumcorite</span> Rare hydrated lead arsenate mineral

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> Rare hydrated zinc arsenate

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">Hidalgoite</span> Mineral of the beudantite group

Hidalgoite, PbAl3(AsO4)(SO4)(OH)4, is a rare member of the beudantite group and is usually classified as part of the alunite family. It was named after the place where it was first discovered, the Zimapán mining district, Hidalgo, Mexico. At Hidalgo where it was initially discovered, it was found as dense white masses in alternating dikes of quartz latite and quartz monzonite alongside other secondary minerals such as sphalerite, arsenopyrite, cerussite and trace amounts of angelsite and alamosite, it was then rediscovered at other locations such as Australia where it occurs on oxidized shear zones above greywacke shales especially on the anticline prospects of the area, and on fine grained quartz-spessartine rocks in Broken Hill, Australia. Hidalgoite specimens are usually associated with copper minerals, clay minerals, iron oxides and polymetallic sulfides in occurrence.

<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">Mottramite</span> Orthorhombic anhydrous vanadate hydroxide mineral

Mottramite is an orthorhombic anhydrous vanadate hydroxide mineral, PbCu(VO4)(OH), at the copper end of the descloizite subgroup. It was formerly called cuprodescloizite or psittacinite (this mineral characterized in 1868 by Frederick Augustus Genth). Duhamelite is a calcium- and bismuth-bearing variety of mottramite, typically with acicular habit.

<span class="mw-page-title-main">Arsendescloizite</span> Lead-zinc mineral

Arsendescloizite is a lead-zinc mineral, approved by the IMA in 1982. It is an arsenate analog of descloizite. Its first description was published in 1982.

Gallobeudantite is a secondary, Gallium-bearing mineral of beudantite, where the Iron is replaced with Gallium, a rare-earth metal. It was first described as a distinct mineral by Jambor et al in 1996. Specific Gallium minerals are generally rare and Gallium itself is usually obtained as a by-product during the processing of the ores of other metals. In particular, the main source material for Gallium is bauxite, a key ore of aluminium. However, Gallobeudantite is too rare to be of economic value. Its main interest is academic and also among mineral collectors.

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 Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. (eds.). Handbook of Mineralogy (PDF). Chantilly, VA 20151-1110, US: Mineralogical Society of America. Retrieved 12 February 2022.{{cite book}}: CS1 maint: location (link)
  3. "Mimetite". Mindat.org . Retrieved 12 February 2021.
  4. Barthelmy, David (2014). "Mimetite Mineral Data". Mineralogy Database. Webmineral.com. Retrieved 12 February 2022.
  5. 1 2 3 4 5 Sinkankas, John (1964). Mineralogy for amateurs. Princeton, N.J.: Van Nostrand. pp. 419–422. ISBN   0442276249.
  6. Burke, E.A.J. (2006). "A mass discreditation of GQN minerals". The Canadian Mineralogist. 44 (6): 1557–1560. Bibcode:2006CaMin..44.1557B. doi:10.2113/gscanmin.44.6.1557.