Ianbruceite
   HOME

TheInfoList



OR:

Ianbruceite is a rare hydrated zinc arsenate with the formula n2(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 Founded in 1958, the International Mineralogical Association (IMA) is an international group of 40 national societies. The goal is to promote the science of mineralogy and to standardize the nomenclature of the 5000 plus known mineral species. Th ...
as a new mineral species in 2011, reference IMA2011-49, and named for Ian Bruce,http://crystalclassics.co.uk/page.php?id=3> 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 High Pike is a fell in the northern part of the English Lake District, it is located 4.5 kilometres south of Caldbeck. It has a height of 658 metres (2159 feet) and is the most northerly of the Lakeland fells over 2000 feet. It is a ...
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).


Structure

There are four formula units per unit cell (Z = 4). 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°. It belongs in the monoclinic,
prismatic An optical prism is a transparent optical element with flat, polished surfaces that are designed to refract light. At least one surface must be angled — elements with two parallel surfaces are ''not'' prisms. The most familiar type of optical ...
crystal Class 2/m, with space group P21/c.
Ianbruceite consists of layers with composition n2(OH)(H2O)(AsO4)alternating with an inter-layer space containing loosely bound
water molecules Water () is a polar inorganic compound that is at room temperature a tasteless and odorless liquid, which is nearly colorless apart from an inherent hint of blue. It is by far the most studied chemical compound and is described as the "univer ...
. The arsenic is
tetrahedrally In a tetrahedral molecular geometry, a central atom is located at the center with four substituents that are located at the corners of a tetrahedron. The bond angles are cos−1(−) = 109.4712206...° ≈ 109.5° when all four substituents are ...
coordinated by four oxygen anions.


Appearance

Ianbruceite occurs as aggregates of tiny, radiating, lath-like crystals with a distinctive diamond-shaped outline, up to 0.2 mm across. Material from Tsumeb is blue, ranging from a very pale color to deep blue. Material from the Caldbeck Fells is white to pale pink. The crystals have a vitreous luster and a white streak.


Optical properties

The refractive indices of ianbruceite are similar to that of ordinary window glass, with nα = 1.601, nβ = 1.660 and nγ = 1.662. 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.Klein and Hurlbut (1993) Manual of Mineralogy 21st Edition. Wiley For ianbruceite 2V is greater for violet light than for red light, v > r. 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°. The mineral does not fluoresce in ultraviolet light.


Physical properties

Cleavage is perfect parallel to (100). Crystals of ianbruceite are flexible and deform plastically. The mineral is very soft, with Mohs hardness only 1, the same as talc. Measurements of the specific gravity have not been reported, but from the formula and the cell dimensions it has been calculated as 3.197. It is insoluble in dilute
acid In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequ ...
, which distinguishes it from hydrozincite and aragonite, which are also
supergene A supergene is a chromosomal region encompassing multiple neighboring genes that are inherited together because of close genetic linkage, i.e. much less recombination than would normally be expected. This mode of inheritance can be due to genomic ...
minerals that form white crusts. The loosely bound water between the layers is easily lost, so the mineral may
effloresce In chemistry, efflorescence (which means "to flower out" in French) is the migration of a salt to the surface of a porous material, where it forms a coating. The essential process involves the dissolving of an internally held salt in water, or ...
. It also readily absorbs
alcohol Alcohol most commonly refers to: * Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom * Alcohol (drug), an intoxicant found in alcoholic drinks Alcohol may also refer to: Chemicals * Ethanol, one of sev ...
.


Occurrence

The type locality is the
Tsumeb Mine , nickname = , settlement_type = City , motto = ''Glück Auf'' (German for ''Good luck'') , image_skyline = Welcome to tsumeb.jpg , imagesize = , image_caption = , image_flag ...
, Otjikoto Region, Namibia. Type material is conserved in the Department of Natural History,
Royal Ontario Museum The Royal Ontario Museum (ROM) is a museum of art, world culture and natural history in Toronto, Ontario, Canada. It is one of the largest museums in North America and the largest in Canada. It attracts more than one million visitors every year ...
, Toronto, Ontario, Canada, catalogue number M53150. At localities in the Caldbeck Fells ianbruceite occurs as a late-stage
supergene A supergene is a chromosomal region encompassing multiple neighboring genes that are inherited together because of close genetic linkage, i.e. much less recombination than would normally be expected. This mode of inheritance can be due to genomic ...
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 High Pike is a fell in the northern part of the English Lake District, it is located 4.5 kilometres south of Caldbeck. It has a height of 658 metres (2159 feet) and is the most northerly of the Lakeland fells over 2000 feet. It is a ...
. Arsenopyrite is abundant there, and its oxidation in veins that also contain primary lead, zinc and copper
sulfides Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to chemical compounds la ...
has produced a range of supergene arsenates. 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 Dolomite may refer to: *Dolomite (mineral), a carbonate mineral *Dolomite (rock), also known as dolostone, a sedimentary carbonate rock *Dolomite, Alabama, United States, an unincorporated community *Dolomite, California, United States, an unincor ...
matrix Matrix most commonly refers to: * ''The Matrix'' (franchise), an American media franchise ** ''The Matrix'', a 1999 science-fiction action film ** "The Matrix", a fictional setting, a virtual reality environment, within ''The Matrix'' (franchis ...
with
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 ...
, chalcopyrite and cobalt-bearing
köttigite 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 (18241892), a German chemist from Schneeberg, Saxony, who made the first chemical analysis of the ...
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 Adamite is a zinc arsenate hydroxide mineral, Zn2 As O4O H. 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 a ...
and an unidentified copper
silicate In chemistry, a silicate is any member of a family of polyatomic anions consisting of silicon and oxygen, usually with the general formula , where . The family includes orthosilicate (), metasilicate (), and pyrosilicate (, ). The name is al ...
. 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 Dolomite may refer to: *Dolomite (mineral), a carbonate mineral *Dolomite (rock), also known as dolostone, a sedimentary carbonate rock *Dolomite, Alabama, United States, an unincorporated community *Dolomite, California, United States, an unincor ...
. One block of material contained abundant marcasite,
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 ...
,
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 ...
and minor fine-grained arsenopyrite, in
dolomitic Dolomite () is an anhydrous carbonate mineral composed of calcium magnesium carbonate, ideally The term is also used for a sedimentary carbonate rock composed mostly of the mineral dolomite. An alternative name sometimes used for the dolomiti ...
matrix. 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 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 (18241892), a German chemist from Schneeberg, Saxony, who made the first chemical analysis of the ...
,
legrandite Legrandite is a rare zinc arsenate mineral, Zn2(AsO4)(OH)·(H2O). It is an uncommon secondary mineral in the oxidized zone of arsenic bearing zinc deposits and occurs rarely in granite pegmatite. Associated minerals include: adamite, paradamit ...
and
adamite Adamite is a zinc arsenate hydroxide mineral, Zn2 As O4O H. 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 a ...
. 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 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 (18241892), a German chemist from Schneeberg, Saxony, who made the first chemical analysis of the ...
, minor
legrandite Legrandite is a rare zinc arsenate mineral, Zn2(AsO4)(OH)·(H2O). It is an uncommon secondary mineral in the oxidized zone of arsenic bearing zinc deposits and occurs rarely in granite pegmatite. Associated minerals include: adamite, paradamit ...
and
adamite Adamite is a zinc arsenate hydroxide mineral, Zn2 As O4O H. 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 a ...
.


References

{{reflist Zinc minerals Arsenates Monoclinic minerals Minerals in space group 14 Minerals described in 2011