Tarbuttite is a rare

phosphate mineral Phosphate minerals contain the tetrahedrally coordinated phosphate (PO43−) anion along sometimes with arsenate (AsO43−) and vanadate (VO43−) substitutions, and chloride (Cl−), fluoride (F−), and hydroxide (OH−) anions that also fit ...

with formula Zn₂(PO₄)(OH). It was discovered in 1907 in what is now Zambia and named for Percy Tarbutt.

Description and habit

Tarbuttite is white, yellow, red, green, brown, or colorless; in

transmitted light Transmittance of the surface of a material is its effectiveness in transmitting radiant energy. It is the fraction of incident electromagnetic power that is transmitted through a sample, in contrast to the transmission coefficient, which is th ...

it is colorless. Traces of copper cause green coloring, while

iron hydroxide Iron oxides are chemical compounds composed of iron and oxygen. Several iron oxides are recognized. All are black magnetic solids. Often they are non-stoichiometric. Oxyhydroxides are a related class of compounds, perhaps the best known of whi ...

s cause the other colors. Colorless crystals tend to be transparent while colored specimens have varying degrees of transparency. The mineral occurs as equant to short prismatic crystals up to , in sheaf-like or saddle-shaped aggregates, or as crusts. Individual crystals are commonly rounded and striated.

Structure

Zinc ions are surrounded by oxygen in a nearly perfect

trigonal bipyramid In geometry, the triangular bipyramid (or dipyramid) is a type of hexahedron, being the first in the infinite set of face-transitive bipyramids. It is the dual of the triangular prism with 6 isosceles triangle faces. As the name suggests, i ...

and phosphate groups are

tetrahedral In geometry, a tetrahedron (plural: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular faces, six straight edges, and four vertex corners. The tetrahedron is the simplest of all the ...

. The

crystal structure In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric patterns ...

consists of zig-zag chains of Zn₁ polyhedra linked by phosphate groups and pairs of Zn₂ polyhedra. In each

unit cell In geometry, biology, mineralogy and solid state physics, a unit cell is a repeating unit formed by the vectors spanning the points of a lattice. Despite its suggestive name, the unit cell (unlike a unit vector, for example) does not necessaril ...

are two

formula unit In chemistry, a formula unit is the empirical formula of any ionic or covalent network solid compound used as an independent entity for stoichiometric calculations. It is the lowest whole number ratio of ions represented in an ionic compound. E ...

s of Zn₂(PO₄)(OH).Cocco, p. 321.

History

Tarbuttite was discovered in 1907 in Broken Hill, Northern Rhodesia, (now

Kabwe Kabwe is the capital of the Zambian Central Province and the Kabwe District, with a population estimated at 202,914 at the 2010 census. Named Broken Hill until 1966, it was founded when lead and zinc deposits were discovered in 1902. Kabwe also ...

, Zambia).Spencer, p. 1. The mineral was described from specimens in cellular limonite in the largest hill of the group,

Kopje An inselberg or monadnock () is an isolated rock hill, knob, ridge, or small mountain that rises abruptly from a gently sloping or virtually level surrounding plain. In Southern Africa a similar formation of granite is known as a koppie, a ...

No. 2.Spencer, p. 2. In a cave discovered in Kopje No. 1 by boring a tunnel, tarbuttite was also found in association with hopeite as obscure crystals and crystals smaller than Spencer, p. 30. and as an encrustation on some bones.Spencer, p. 31. Several specimens of the mineral were collected by Percy Coventry Tarbutt, a director of the Broken Hill Exploration Company.Spencer, p. 22. In 1907, the name ''tarbuttite'' was proposed by L.J. Spencer in the journal ''

Nature Nature, in the broadest sense, is the physical world or universe. "Nature" can refer to the phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. Although humans are ...

'' in honor of Tarbutt. When the International Mineralogical Association was founded, tarbuttite was

grandfathered A grandfather clause, also known as grandfather policy, grandfathering, or grandfathered in, is a provision in which an old rule continues to apply to some existing situations while a new rule will apply to all future cases. Those exempt from t ...

as a valid mineral species.

Occurrence

Tarbuttite has been found in Algeria, Angola, Australia, Canada, China, Namibia, the United States, and Zambia. Tarbuttite forms as secondary mineral in oxidized zinc deposits. It has been found in association with

cerussite Cerussite (also known as lead carbonate or white lead ore) is a mineral consisting of lead carbonate (PbCO3), and is an important ore of lead. The name is from the Latin ''cerussa'', white lead. ''Cerussa nativa'' was mentioned by Conrad Gessner ...

descloizite Descloizite is a rare mineral species consisting of basic lead and zinc vanadate, , crystallizing in the orthorhombic crystal system and isomorphous with olivenite. Appreciable gallium and germanium may also be incorporated into the crystal struc ...

hemimorphite 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 ...

hopeite Hopeite is a hydrated zinc phosphate with formula: Zn3(PO4)2·4H2O. It is a rare mineral used mainly as a collectors specimen. Hopeite crystallizes in the orthorhombic system with prism (geometry), prismatic, Glass, vitreous white to yellow crys ...

hydrozincite Hydrozincite, also known as zinc bloom or marionite, is a white carbonate mineral consisting of Zn5( CO3)2( OH)6. It is usually found in massive rather than crystalline form. It occurs as an oxidation product of zinc ores and as post mine incru ...

, " limonite", parahopeite,

pyromorphite Pyromorphite is a mineral species composed of lead chlorophosphate: Pb5( P O4)3 Cl, 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 pl ...

, scholzite,

smithsonite Smithsonite, also known as zinc spar, is the mineral form of zinc carbonate ( Zn CO3). Historically, smithsonite was identified with hemimorphite before it was realized that they were two different minerals. The two minerals are very similar in a ...

, and

vanadinite Vanadinite is a mineral belonging to the apatite group of phosphates, with the chemical formula Pb5( V O4)3 Cl. 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 f ...

References

Bibliography

* *Palache, P.; Berman H.; Frondel, C. (1960). "''Dana's System of Mineralogy, Volume II: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, Etc. (Seventh Edition)"'' John Wiley and Sons, Inc., New York, pp. 869–871. *

External links

{{commonscat-inline, Tarbuttite Triclinic minerals Zinc minerals Phosphate minerals Hydroxide minerals Minerals in space group 2 Minerals described in 1907