Hemihedrite
(repeating unit)Pb10Zn(CrO4)6(SiO4)2(F,OH)2 IMA symbol Hhe[1] Strunz classification 7.FC.15 Crystal system Triclinic Space group P1 (No. 2) Unit cell a = 9.49, b = 11.44
c = 10.84 [Å]; α = 120.5°
β = 92.1°, γ = 55.83°; Z = 1 Identification Color Bright orange, henna-brown, to almost black Crystal habit Euhedral crystals with hemihedral morphology Twinning Present Mohs scale hardness 3 Luster Vitreous Streak Saffron-yellow Diaphaneity Translucent to transparent Specific gravity 6.42 Optical properties Biaxial (+) Refractive index nα = 2.105 nβ = 2.320 nγ = 2.650 Birefringence δ = 0.545 Pleochroism Feeble, yellow to orange 2V angle 88° (measured) References [2][3][4][5][6]
c = 10.84 [Å]; α = 120.5°
β = 92.1°, γ = 55.83°; Z = 1
Hemihedrite is a rare lead zinc chromate silicate mineral with formula Pb10Zn(CrO4)6(SiO4)2(F,OH)2. It forms a series with the copper analogue iranite.[3]
Discovery and occurrence
Hemihedrite was first described in 1967 for occurrences in the Florence lead silver mine in the Ripsey District, Tortilla Mountains, Pinal County, Arizona, US.[3] It was named for the hemihedral morphology of its crystals.[2]
It occurs in oxidized veins containing galena, sphalerite and pyrite. Associated secondary minerals include cerussite, phoenicochroite, vauquelinite, willemite, wulfenite, galena, sphalerite, pyrite, tennantite and chalcopyrite.[2] It has been reported from several mining districts in Arizona and one in Nevada. It has also been reported from the Antofagasta Region of Chile and the Anarak District of Esfahan Province, Iran.[3]
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.
- ^ a b c Handbook of Mineralogy
- ^ a b c d Hemihedrite on Mindat.org
- ^ Hemihedrite data on Webmineral
- ^ Mineralienatlas
- ^ McLean, W.J.; Anthony, J.W. (1970). "The crystal structure of hemihedrite". American Mineralogist. 55: 1103–1114.
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