Tarbuttite

Phosphate mineral
(repeating unit)Zn2(PO4)(OH)IMA symbolTbt[1]Strunz classification8.BB.35Dana classification41.6.7.1Crystal systemTriclinicCrystal classPinacoidal (1)
(same H-M symbol)Space groupP1Unit cella = 5.400 Å, b = 5.654 Å
c = 6.465 Å, α = 102.51°
β = 102.46°, γ = 86.50°
Z = 2[2]IdentificationColorWhite, colorless, yellow, red, green, or brownCrystal habitEquant to short prismatic [001], sheaf-like aggregates, crusts, individual crystals rounded and deeply striatedCleavagePerfect on {010}FractureIrregular, unevenMohs scale hardness3.5LusterVitreous, pearly on cleavages[2]StreakWhiteDiaphaneityTransparent, translucentSpecific gravity4.12; 4.19 (calc.)Density4.12 g/cm3 (measured)Optical propertiesBiaxial (−)Refractive indexnα = 1.660
nβ = 1.705
nγ = 1.713Birefringenceδ = 0.0532V angle50° (measured)DispersionWeak,[3] strong[2]Ultraviolet fluorescenceNon-fluorescent[4]References[3]

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.

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

  1. ^ 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.
  2. ^ a b c d e f "Tarbuttite" (PDF). Handbook of Mineralogy. Mineral Data Publishing. Retrieved July 13, 2012.
  3. ^ a b c d e f g "Tarbuttite". Mindat. Retrieved July 13, 2012.
  4. ^ "Tarbuttite". Webmineral. Retrieved July 13, 2012.
  5. ^ a b c Spencer, p. 22.
  6. ^ Cocco, p. 321.
  7. ^ a b Spencer, p. 1.
  8. ^ a b Spencer, p. 2.
  9. ^ a b Spencer, p. 30.
  10. ^ 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. 15 (68). The Mineralogical Society: 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. 23 (12). Mineralogical Society of America: 881–893.

External links

Media related to Tarbuttite at Wikimedia Commons