Crocoite

Crocoite
Crocoite
	Crocoite from Dundas, Tasmania
General
Category	Chromate minerals
Formula; (repeating unit)	Lead Chromate PbCrO4
IMA symbol	Crc
Strunz classification	7.FA.20
Crystal system	Monoclinic
Crystal class	Prismatic (2/m); (same H-M symbol)
Space group	P21/n
Unit cell	a = 7.12 Å, b = 7.421 Å,; c = 6.8 Å; β = 102.41°; Z = 4
Identification
Color	Orange, red, yellow; orange-red in transmitted light.
Crystal habit	Coarsely crystalline to acicular
Cleavage	Distinct on {110} indistinct on {001} and {100}
Fracture	Conchoidal to uneven
Tenacity	Sectile
Mohs scale hardness	2.5–3
Luster	Adamantine, Sub-Adamantine, Sub-Vitreous, Resinous, Waxy
Streak	Yellowish orange
Diaphaneity	Transparent to translucent
Specific gravity	5.9–6.1
Optical properties	Biaxial (+)
Refractive index	nα = 2.290(2) nβ = 2.360(2) nγ = 2.660(2)
Birefringence	δ = 0.370
Pleochroism	Weak
References

Crocoite is a mineral consisting of lead chromate, Pb Cr O₄, and crystallizing in the monoclinic crystal system. It is identical in composition with the artificial product chrome yellow used as a paint pigment.^[5]

^ 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.
^ "Crocoite (PbCrO4)" (PDF). Rruff.geo.arizona.edu. Retrieved 19 December 2016.
^ "Crocoite: Crocoite mineral information and data". Mindat.org. 15 December 2016. Retrieved 19 December 2016.
^ "Crocoite Mineral Data". Webmineral.com. Retrieved 19 December 2016.
^ Chisholm 1911.