Pseudomalachite | |
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General | |
Category | Phosphate minerals |
Formula (repeating unit) | Cu5(PO4)2(OH)4 |
IMA symbol | Pmlc [1] |
Strunz classification | 8.BD.05 |
Dana classification | 41.04.03.01 |
Crystal system | Monoclinic |
Crystal class | Prismatic (2/m) (same H-M symbol) |
Space group | P21/c |
Unit cell | a = 4.47 Å, b = 5.75 Å, c = 17.05 Å; β = 91.06°; Z = 2 |
Identification | |
Formula mass | 575.7 g/mol |
Color | Dark emerald green to blackish green |
Crystal habit | Crystals, which are rare, are prismatic, usually with uneven faces. Pseudomalachite is commonly compact, reniform or botryoidal, or it may be fibrous or in crusts and films. |
Twinning | On {100} |
Cleavage | Perfect on {100}, distinct on {010} |
Fracture | Splintery or conchoidal |
Mohs scale hardness | 4.5–5 |
Luster | Vitreous |
Streak | Blue green, paler than the mineral |
Diaphaneity | Translucent to subtranslucent |
Specific gravity | (Measured) 4.15 to 4.35 |
Optical properties | Biaxial (−) |
Refractive index | nα = 1.791 nβ = 1.856 nγ = 1.867 |
Birefringence | δ = 0.076 |
Pleochroism | Weak; X = bluish green to pale green; Y = yellowish green; Z = deep bluish green to blue-green |
2V angle | 48° |
Dispersion | Strong r<v. Also biaxial (+) r>v |
Solubility | Soluble in acids but without effervescence (in contrast to malachite which effervesces with warm HCl) |
Other characteristics | Not fluorescent, not radioactive |
References | [2] [3] [4] [5] |
Pseudomalachite is a phosphate of copper with hydroxyl, named from the Greek for "false" and "malachite", because of its similarity in appearance to the carbonate mineral malachite, Cu2(CO3)(OH)2. Both are green coloured secondary minerals found in oxidised zones of copper deposits, often associated with each other. Pseudomalachite is polymorphous with reichenbachite and ludjibaite. It was discovered in 1813. Prior to 1950 it was thought that dihydrite, lunnite, ehlite, tagilite and prasin were separate mineral species, but Berry analysed specimens labelled with these names from several museums, and found that they were in fact pseudomalachite. The old names are no longer recognised by the IMA. [6]
The type locality is the Virneberg Mine, Rheinbreitbach, Westerwald, Rhineland-Palatinate, Germany. This is an area of ancient copper mining dating back to Roman times, and worked intermittently up until 1872. [2] The type material is held at the Mining Academy, Freiberg, Germany. [4]
The copper ions are co-ordinated by six oxygen ions to form distorted octahedra. [7] These octahedra are linked by sharing edges to form two distinct types of infinite chains, parallel to b. The chains are linked alternately, again by sharing octahedral edges, to form sheets parallel to the bc plane. Distorted phosphate tetrahedra link the sheets, and there is some doubt about the exact position of the hydrogen ions in the structure. [8]
It is a secondary mineral found in the oxidised zones of copper ore deposits. Associated with libethenite at several localities in New South Wales, Australia, [9] and at the Chino Mine, New Mexico, US. [10] Other associated minerals are apatite, azurite, chalcedony, chrysocolla, cornetite, cuprite, malachite, pyromorphite, tenorite, and iron oxyhydroxides.
Pseudomalachite has been reported from Argentina, Australia, Austria, Belgium, Brazil, Canada, Chile, Czech Republic, Democratic Republic of Congo, France, Germany, Ireland, Israel, Italy, Japan, Kazakhstan, Madagascar, Mexico, Namibia, Norway, Poland, Portugal, Republic of Congo, Romania, Russia, Slovakia, South Africa, Spain, UK, US and Zambia.
Germanite is a rare copper iron germanium sulfide mineral, Cu26Fe4Ge4S32. It was first discovered in 1922, and named for its germanium content. It is only a minor source of this important semiconductor element, which is mainly derived from the processing of the zinc sulfide mineral sphalerite. Germanite contains gallium, zinc, molybdenum, arsenic, and vanadium as impurities.
Malachite is a copper carbonate hydroxide mineral, with the formula Cu2CO3(OH)2. This opaque, green-banded mineral crystallizes in the monoclinic crystal system, and most often forms botryoidal, fibrous, or stalagmitic masses, in fractures and deep, underground spaces, where the water table and hydrothermal fluids provide the means for chemical precipitation. Individual crystals are rare, but occur as slender to acicular prisms. Pseudomorphs after more tabular or blocky azurite crystals also occur.
Aurichalcite is a carbonate mineral, usually found as a secondary mineral in copper and zinc deposits. Its chemical formula is (Zn,Cu)5(CO3)2(OH)6. The zinc to copper ratio is about 5:4. Copper (Cu2+) gives aurichalcite its green-blue colors.
Dioptase is an intense emerald-green to bluish-green copper cyclosilicate mineral. It is transparent to translucent. Its luster is vitreous to sub-adamantine. Its formula is Cu6Si6O18·6H2O (also reported as CuSiO2(OH)2). It has a hardness of 5, the same as tooth enamel. Its specific gravity is 3.28–3.35, and it has two perfect and one very good cleavage directions. Additionally, dioptase is very fragile, and specimens must be handled with great care. It is a trigonal mineral, forming 6-sided crystals that are terminated by rhombohedra.
Torbernite, also known as chalcolite, is a relatively common mineral with the chemical formula Cu[(UO2)(PO4)]2(H2O)12. It is a radioactive, hydrated green copper uranyl phosphate, found in granites and other uranium-bearing deposits as a secondary mineral. The chemical formula of torbernite is similar to that of autunite in which a Cu2+ cation replaces a Ca2+ cation. Torbernite tends to dehydrate to metatorbernite with the sum formula Cu[(UO2)(PO4)]2(H2O)8.
Liroconite is a complex mineral: Hydrated copper aluminium arsenate hydroxide, with the formula Cu2Al[(OH)4|AsO4]·4(H2O). It is a vitreous monoclinic mineral, colored bright blue to green, often associated with malachite, azurite, olivenite, and clinoclase. It is quite soft, with a Mohs hardness of 2–2.5, and has a specific gravity of 2.9–3.0.
Vauxite is a phosphate mineral with the chemical formula Fe2+Al2(PO4)2(OH)2·6(H2O). It belongs to the laueite – paravauxite group, paravauxite subgroup, although Mindat puts it as a member of the vantasselite Al4(PO4)3(OH)3·9H2O group. There is no similarity in structure between vauxite and paravauxite Fe2+Al2(PO4)2(OH)2·8H2O or metavauxite Fe3+Al2(PO4)2(OH)2·8H2O, even though they are closely similar chemically and all minerals occur together as secondary minerals. Vauxite was named in 1922 for George Vaux Junior (1863–1927), an American attorney and mineral collector.
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.
Bergenite is a rare uranyl phosphate of the more specific phosphuranylite group. The phosphuranylite-type sheet in bergenite is a new isomer of the group, with the uranyl phosphate tetrahedra varying in an up-up-down, same-same-opposite (uuduudSSOSSO) orientation. All bergenite samples have been found in old mine dump sites. Uranyl minerals are a large constituent of uranium deposits.
Népouite is a rare nickel silicate mineral which has the apple green color typical of such compounds. It was named by the French mining engineer Edouard Glasser in 1907 after the place where it was first described, the Népoui Mine, Népoui, Poya Commune, North Province, New Caledonia. The ideal formula is Ni3(Si2O5)(OH)4, but most specimens contain some magnesium, and (Ni,Mg)3(Si2O5)(OH)4 is more realistic. There is a similar mineral called lizardite in which all of the nickel is replaced by magnesium, formula Mg3(Si2O5)(OH)4. These two minerals form a series; intermediate compositions are possible, with varying proportions of nickel to magnesium.
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.
Lavendulan is an uncommon copper arsenate mineral, known for its characteristic intense electric blue colour. It belongs to the lavendulan group, which has four members:
Cornubite is a rare secondary copper arsenate mineral with formula: Cu5(AsO4)2(OH)4. 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. It is a dimorph of cornwallite, and the arsenic analogue of pseudomalachite.
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.
Satterlyite is a hydroxyl bearing iron phosphate mineral. The mineral can be found in phosphatic shales and was first discovered in the Big Fish River area in Yukon Territory, Canada.
Cornwallite is an uncommon copper arsenate mineral with formula Cu5(AsO4)2(OH)4. It forms a series with the phosphate pseudomalachite and is a dimorph of the triclinic cornubite. It is a green monoclinic mineral which forms as radial to fibrous encrustations.
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.
Marshite (CuI) is a naturally occurring isometric halide mineral with occasional silver (Ag) substitution for copper (Cu). Solid solution between the silver end-member miersite and the copper end-member marshite has been found in these minerals from deposits in Broken Hill, Australia. The mineral's name is derived from the person who first described it, an Australian mineral collector named Charles W. Marsh. Marsh drew attention to native copper iodide (Marshite) in the 1800s emphasizing its natural occurrence, it is not to be confused with copper (I) iodide a substance commonly synthesized in laboratory settings.
Cornetite is a phosphate of copper with hydroxyl, named after the geologist Jules Cornet. It was discovered in 1917.
Falsterite is a rare phosphate mineral with the formula Ca2MgMn2+2(Fe2+0.5Fe3+0.5)4Zn4(PO4)8(OH)4(H2O)14. It is a pegmatitic mineral, related to the currently approved mineral ferraioloite.