Ianbruceite | |
---|---|
General | |
Category | Zinc arsenates |
Formula (repeating unit) | [Zn2(OH)(H2O)(AsO4)](H2O)2 |
IMA symbol | Ibc [1] |
Strunz classification | 8.DA.50 |
Dana classification | 42 (hydrated phosphates, arsenates and vanadates containing hydroxyl or halogen) |
Crystal system | Monoclinic |
Crystal class | Prismatic (2/m) (same H-M symbol) |
Space group | P21/b |
Identification | |
Color | Sky blue to very pale blue at Tsumeb, white to pale pink in the Caldbeck Fells |
Crystal habit | Radiating aggregates of lath-like crystals with a distinctive diamond-shaped outline {100} |
Cleavage | Perfect parallel to (100) |
Fracture | Crystals are flexible and deform plastically |
Mohs scale hardness | 1 |
Luster | Vitreous |
Streak | White |
Specific gravity | Calculated, 3.197 |
Optical properties | Biaxial |
Refractive index | nα = 1.601, nβ = 1.660, nγ = 1.662 |
Solubility | Insoluble in dilute acid |
Other characteristics | It may dehydrate, and it can readily absorb alcohol. Not fluorescent under ultraviolet light |
References | [2] [3] [4] [5] |
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. [2] [5] 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, [6] 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. [5] Caldbeck Fells and Tsumeb are the only reported localities for ianbruceite to date (May 2013).
There are four formula units per unit cell (Z = 4). [3] Unit cell parameters are the lengths of the sides of the unit cell, a, b and c, and the angle β between the a and c crystal axes. For ianbruceite a = 11.793 Å, b = 9.1138 Å, c = 6.8265 Å, and β = 103.859°. [2] [3] [4] It belongs in the monoclinic, prismatic crystal Class 2/m, with space group P21/c. [2] [3] [4]
Ianbruceite consists of layers with composition [Zn2(OH)(H2O)(AsO4)] alternating with an inter-layer space containing loosely bound water molecules. [5] The arsenic is tetrahedrally coordinated by four oxygen anions.
Ianbruceite occurs as aggregates of tiny, radiating, lath-like crystals with a distinctive diamond-shaped outline, up to 0.2 mm across. [5] Material from Tsumeb is blue, ranging from a very pale color to deep blue. [3] Material from the Caldbeck Fells is white to pale pink. [5] The crystals have a vitreous luster and a white streak.
The refractive indices of ianbruceite are similar to that of ordinary window glass, with nα = 1.601, nβ = 1.660 and nγ = 1.662. [3] The refractive index varies with the wavelength (color) of light, so the positions of the optic axes in biaxial crystals, and the angle 2V between them, will change when the color of the incident light is changed. This effect may be expressed in the form r > v, indicating that the angle 2V is greater for red than for violet light, or vice versa. [7] For ianbruceite 2V is greater for violet light than for red light, v > r. [3] The angle 2V has been measured as 18°; it can also be calculated from the values of the refractive indices α, β and γ, giving a value of 20°. [3] The mineral does not fluoresce in ultraviolet light. [2] [3]
Cleavage is perfect parallel to (100). [2] [3] [5] Crystals of ianbruceite are flexible and deform plastically. [3] [5] The mineral is very soft, with Mohs hardness only 1, the same as talc. [2] [3] Measurements of the specific gravity have not been reported, but from the formula and the cell dimensions it has been calculated as 3.197. [2] [3] It is insoluble in dilute acid, which distinguishes it from hydrozincite and aragonite, which are also supergene minerals that form white crusts. [5] The loosely bound water between the layers is easily lost, so the mineral may effloresce. It also readily absorbs alcohol. [5]
The type locality is the Tsumeb Mine, Otjikoto Region, Namibia. [2] Type material is conserved in the Department of Natural History, Royal Ontario Museum, Toronto, Ontario, Canada, catalogue number M53150. [4]
At localities in the Caldbeck Fells ianbruceite occurs as a late-stage supergene mineral in fractures in partly oxidised sulfide-rich carbonate or quartz-carbonate matrix. The mines of Caldbeck Fells are famous for their supergene minerals. Driggith and Potts Gill Mines worked low temperature lead-zinc-copper veins on the eastern and northern slopes of High Pike. Arsenopyrite is abundant there, and its oxidation in veins that also contain primary lead, zinc and copper sulfides has produced a range of supergene arsenates. [5]
At the Driggith Mine, Caldbeck Fells, Cumbria, on dumps from the 30 fathom level, radiating aggregates of lath-like crystals of ianbruceite have been found in fractures in quartz-dolomite matrix with sphalerite, chalcopyrite and cobalt-bearing köttigite as rounded pink aggregates, or more rarely pale pink to colorless monoclinic blades, as well as irregular black patches of a cobalt-bearing manganese oxide, adamite and an unidentified copper silicate. [5] At the nearby Potts Gill Mine, Caldbeck Fells, Cumbria, on dumps from the Endeavor level, it has been found as minute, pearly, lath-like crystals in fractures in arsenopyrite-rich dolomite. One block of material contained abundant marcasite, galena, sphalerite and minor fine-grained arsenopyrite, in dolomitic matrix. [5]
In Namibia ianbruceite has been found in the zinc pocket at the 44 Level, Tsumeb Mine, as sky blue to very pale blue platy crystals associated with leiteite, köttigite, legrandite and adamite. [5] It occurs as thin platy crystals up to 80 μm long and a few μm thick, which form flattened aggregates up to 0.10 mm across, and ellipsoidal aggregates up to 0.5 mm across, associated with coarse white leiteite, dark blue köttigite, minor legrandite and adamite. [3]
Hemimorphite is the chemical compound Zn4(Si2O7)(OH)2·H2O, a component of mineral calamine. It is a silicate mineral which, together with smithsonite (ZnCO3), has been historically mined from the upper parts of zinc and lead ores. Both compounds were originally believed to be the same mineral and classified as calamine. In the second half of the 18th century, it was discovered that these two different compounds were both present in calamine. They closely resemble one another.
Erythrite or red cobalt is a secondary hydrated cobalt arsenate mineral with the formula Co
3(AsO
4)
2•8H
2O. Erythrite and annabergite, chemical formula Ni
3(AsO
4)
2•8H
2O, or nickel arsenate form a complete series with the general formula (Co,Ni)
3(AsO
4)
2•8H
2O.
Adamite is a zinc arsenate hydroxide mineral, Zn2AsO4OH. It is a mineral that typically occurs in the oxidized or weathered zone above zinc ore occurrences. Pure adamite is colorless, but usually it possess yellow color due to Fe compounds admixture. Tints of green also occur and are connected with copper substitutions in the mineral structure. Olivenite is a copper arsenate that is isostructural with adamite and there is considerable substitution between zinc and copper resulting in an intermediate called cuproadamite. Zincolivenite is a recently discovered mineral being an intermediate mineral with formula CuZn(AsO4)(OH). Manganese, cobalt, and nickel also substitute in the structure. An analogous zinc phosphate, tarbuttite, is known.
Olivenite is a copper arsenate mineral, formula Cu2AsO4OH. It crystallizes in the monoclinic system (pseudo-orthorhombic), and is sometimes found in small brilliant crystals of simple prismatic habit terminated by domal faces. More commonly, it occurs as globular aggregates of acicular crystals, these fibrous forms often having a velvety luster; sometimes it is lamellar in structure, or soft and earthy.
Austinite is a member of the adelite-descloizite group, adelite subgroup, the zinc (Zn) end member of the copper-Zn series with conichalcite. It is the zinc analogue of cobaltaustinite and nickelaustinite. At one time “brickerite” was thought to be a different species, but it is now considered to be identical to austinite. Austinite is named in honour of Austin Flint Rogers (1877–1957), American mineralogist from Stanford University, California, US.
Legrandite is a rare zinc arsenate mineral, Zn2(AsO4)(OH)·(H2O).
Reinerite is a rare arsenite (arsenate(III)) mineral with chemical formula Zn3(AsO3)2. It crystallizes in the orthorhombic crystal system.
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.
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.
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:
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.
Keyite is a mineral with the chemical formula Cu2+3Zn4Cd2(AsO4)6 · 2H2O. The name comes from Charles Locke Key, an American mineral dealer who furnished its first specimens. Keyite is monoclinic-prismatic, meaning its crystal form has three unequal axes, two of which have 90° angles between them and one with an angle less than 90°. Keyite belongs to the biaxial optical class, meaning it has more than one axis of anisotropy, in which light travels with zero birefringence, and three indices of refraction, nα = 1.800, nβ, and nγ = 1.870. Being a very rare cadmium copper arsenate, keyite is only found in Tsumeb, Namibia in the Tsumeb mine, a world-famous copper mine known for its abundance of rare and unusual minerals.
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 dolosmite 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.
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.
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.
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.
Serpierite (Ca(Cu,Zn)4(SO4)2(OH)6·3H2O) is a rare, sky-blue coloured hydrated sulfate mineral, often found as a post-mining product. It is a member of the devilline group, which has members aldridgeite (Cd,Ca)(Cu,Zn)4(SO4)2(OH)6·3H2O, campigliaite Cu4Mn2+(SO4)2(OH)6·4H2O, devilline CaCu4(SO4)2(OH)6·3H2O, kobyashevite Cu5(SO4)2(OH)6·4H2O, lautenthalite PbCu4(SO4)2(OH)6·3H2O and an unnamed dimorph of devilline. It is the calcium analogue of aldridgeite and it is dimorphous with orthoserpierite CaCu4(SO4)2(OH)6·3H2O.
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.
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.
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.