Corkite

Corkite
General
Category Phosphate minerals
Formula
(repeating unit)		 PbFe3[(OH)6:SO4:PO4]
Strunz classification 08.BL.05
Dana classification 43.4.1.2
Crystal symmetry Trigonal hemimorphic (3 2/m)
Unit cell a = 7.3065(5) Å, c = 16.897(2) Å; V 781.2 ų; Z = 3
Identification
Formula mass 667.82 g
Color Brown to light yellowish brown, pale yellow, yellowish green to dark green
Crystal habit Crystals pseudocubic rhombohedral with prominent {1011}. Commonly in crusts and massive
Crystal system Trigonal
Cleavage Perfect on {0001}
Mohs scale hardness 3.5 - 4.5
Luster Vitreous, resinous
Diaphaneity transparent
Specific gravity 4.295 (measured), 4.31 (calculated)
Optical properties uniaxial (-), may appear anomalously biaxial
Refractive index nω = 1.930 nε = 1.930 n = 1.93 - 1.96
Birefringence δ = 0.000
Other characteristics Readily soluble in warm HCl
References [1][2][3][4]

Corkite is a phosphate mineral in the beudantite subgroup of the alunite group. Corkite is the phosphate analogue of beudantite and with it, a complete solid solution range exists. Corkite will also form a solid solution with kintoreite.

Corkite is named after County Cork, Ireland; the location where the first notable amount was discovered in 1869.[1] Like many of the other minerals in the beudantite group, corkite is a relatively uncommon, secondary mineral that occurs in oxidation zones near hydrothermal base metal deposits.[1] It occurs associated with pyromorphite, malachite, plumbojarosite, limonite and quartz.[4]

References

  1. 1 2 3 Mindat.org http://www.mindat.org/min-1130.html
  2. ↑ Webmineral.com http://webmineral.com/data/Corkite.shtml
  3. ↑ EuroMin.net http://euromin.w3sites.net//mineraux/CORKITE.html
  4. 1 2 Handbook of Mineralogy


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