Tarbuttite is a rare

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

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

Description and habit

Tarbuttite is white, yellow, red, green, brown, or colorless; in transmitted light it is colorless. Traces of copper cause green coloring, while

iron hydroxide An iron oxide is a chemical compound composed of iron and oxygen. Several iron oxides are recognized. Often they are non-stoichiometric. Ferric oxyhydroxides are a related class of compounds, perhaps the best known of which is rust. Iron oxide ...

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 A triangular bipyramid is a hexahedron with six triangular faces constructed by attaching two tetrahedra face-to-face. The same shape is also known as a triangular dipyramid or trigonal bipyramid. If these tetrahedra are regular, all faces of a t ...

and phosphate groups are

tetrahedral In geometry, a tetrahedron (: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular Face (geometry), faces, six straight Edge (geometry), edges, and four vertex (geometry), vertices. The tet ...

. The

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

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 In mathematics, a unit vector i ...

are two

formula unit In chemistry, a formula unit is the smallest unit of a non-molecular substance, such as an ionic compound, covalent network solid, or metal. It can also refer to the chemical formula for that unit. Those structures do not consist of discrete mol ...

s of Zn₂(PO₄)(OH).Cocco, p. 321.

History

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

Kabwe Kabwe is the capital of the Zambian Central Province and the Kabwe District, with a population estimated at 288,598 at the 2022 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 Limonite () is an iron ore consisting of a mixture of hydrated iron(III) oxide-hydroxides in varying composition. The generic formula is frequently written as , although this is not entirely accurate as the ratio of oxide to hydroxide can vary qu ...

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, an ...

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 is an inherent character or constitution, particularly of the Ecosphere (planetary), ecosphere or the universe as a whole. In this general sense nature refers to the Scientific law, laws, elements and phenomenon, phenomena of the physic ...

'' in honor of Tarbutt. When 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. ...

was founded, tarbuttite was grandfathered 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 with the chemical formula PbCO3, and is an important ore of lead. The name is from the Latin ''cerussa'', white lead. ''Cerussa nativa'' was ...

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

hemimorphite Hemimorphite is the chemical compound Zinc, Zn4(Pyrosilicate, Si2O7)(Hydroxide, OH)2Water of crystallization, ·H2O, a component of mineral Calamine (mineral), calamine. It is a silicate mineral which, together with smithsonite (ZnCO3), has bee ...

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 inc ...

, "

", 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 p ...

, 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 Phosphate minerals, phosphates, with the chemical formula lead, Pb5(vanadium, Voxygen, O4)3chlorine, Cl. It is one of the main industrial ores of the metal vanadium and a minor source of ...

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