Tarbuttite
Tarbuttite is a rare phosphate mineral with formula Zn2(PO4)(OH). It was discovered in 1907 in what is now Zambia and named for Percy Coventry Tarbutt.
| Tarbuttite | |
|---|---|
 Tarbuttite from Broken Hill mine (Kabwe mine) in Central Province, Zambia | |
| General | |
| Category | Phosphate minerals |
| Formula (repeating unit) | Zn2(PO4)(OH) |
| IMA symbol | Tbt[1] |
| Strunz classification | 8.BB.35 |
| Dana classification | 41.6.7.1 |
| Crystal system | Triclinic |
| Crystal class | Pinacoidal (1) (same H-M symbol) |
| Space group | P1 |
| Unit cell | a = 5.400 Å, b = 5.654 Å c = 6.465 Å, α = 102.51° β = 102.46°, γ = 86.50° Z = 2[2] |
| Identification | |
| Color | White, colorless, yellow, red, green, or brown |
| Crystal habit | Equant to short prismatic [001], sheaf-like aggregates, crusts, individual crystals rounded and deeply striated |
| Cleavage | Perfect on {010} |
| Fracture | Irregular, uneven |
| Mohs scale hardness | 3.5 |
| Luster | Vitreous, pearly on cleavages[2] |
| Streak | White |
| Diaphaneity | Transparent, translucent |
| Specific gravity | 4.12; 4.19 (calc.) |
| Density | 4.12 g/cm3 (measured) |
| Optical properties | Biaxial (-) |
| Refractive index | nα = 1.660 nβ = 1.705 nγ = 1.713 |
| Birefringence | δ = 0.053 |
| 2V angle | 50° (measured) |
| Dispersion | Weak,[3] strong[2] |
| Ultraviolet fluorescence | Non-fluorescent[4] |
| References | [3] |
Description and habit
Tarbuttite is white, yellow, red, green, brown, or colorless; in transmitted light it is colorless.[3] Traces of copper cause green coloring, while iron hydroxides cause the other colors. Colorless crystals tend to be transparent while colored specimens have varying degrees of transparency.[5]
The mineral occurs as equant to short prismatic crystals up to 2 cm (0.79 in), in sheaf-like or saddle-shaped aggregates, or as crusts.[2] Individual crystals are commonly rounded and striated.[3]
Structure
Zinc ions are surrounded by oxygen in a nearly perfect trigonal bipyramid and phosphate groups are tetrahedral. The crystal structure consists of zig-zag chains of Zn1 polyhedra linked by phosphate groups and pairs of Zn2 polyhedra. In each unit cell are two formula units of Zn2(PO4)(OH).[6]
History
Tarbuttite was discovered in 1907 in Broken Hill mine, Northern Rhodesia, (now Kabwe, Zambia).[3][7] The mineral was described from specimens in cellular limonite in the largest hill of the group, Kopje No. 2.[8][9] In a cave discovered in Kopje No. 1 by boring a tunnel,[7] tarbuttite was also found in association with hopeite as obscure crystals and crystals smaller than 1⁄16 mm (0.0025 in)[9] and as an encrustation on some bones.[10] Several specimens of the mineral were collected by Percy Coventry Tarbutt, a director of the Broken Hill Exploration Company.[5][8] In 1907, the name tarbuttite was proposed by L.J. Spencer in the journal Nature in honor of Tarbutt.[5]
When the International Mineralogical Association was founded, tarbuttite was grandfathered as a valid mineral species.[3]
Occurrence
Tarbuttite has been found in Algeria, Angola, Australia, Canada, China, Namibia, the United States, and Zambia.[2][3]
Tarbuttite forms as secondary mineral in oxidized zinc deposits. It has been found in association with cerussite, descloizite, hemimorphite, hopeite, hydrozincite, "limonite", parahopeite, pyromorphite, scholzite, smithsonite, and vanadinite.[2]
See also
References
- Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- "Tarbuttite" (PDF). Handbook of Mineralogy. Mineral Data Publishing. Retrieved July 13, 2012.
- "Tarbuttite". Mindat. Retrieved July 13, 2012.
- "Tarbuttite". Webmineral. Retrieved July 13, 2012.
- Spencer, p. 22.
- Cocco, p. 321.
- Spencer, p. 1.
- Spencer, p. 2.
- Spencer, p. 30.
- Spencer, p. 31.
Bibliography
- Cocco, G.; Fanfani, L.; Zanazzi, P. F. (1966). "The crystal structure of tarbuttite, Zn2(ОH)РО4" (PDF). Zeitschrift für Kristallographie. 123 (5): 321–329. doi:10.1524/zkri.1966.123.16.321. S2CID 96221726.
- 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.
- Spencer, L. J. (April 1908). "On Hopeite and other zinc phosphates and associated minerals from the Broken Hill mines, North-Western Rhodesia" (PDF). Mineralogical Magazine. The Mineralogical Society. 15 (68): 1–38. Bibcode:1908MinM...15....1S. doi:10.1180/minmag.1908.015.68.02.
Further reading
- Richmond, Wallace E. (December 1938). "Tarbuttite" (PDF). American Mineralogist. Mineralogical Society of America. 23 (12): 881–893.
External links
Media related to Tarbuttite at Wikimedia Commons