Lópezite

Lópezite
General
Category	Sulfate minerals (chromate)
Formula (repeating unit)	K2Cr2O7
IMA symbol	Lpz[1]
Strunz classification	7.FD.05
Dana classification	35.2.1.1 Anhydrous chromates
Crystal system	Triclinic
Crystal class	Pinacoidal (1) (same H-M symbol)
Space group	P1
Identification
Color	Orange-red, red
Crystal habit	Granular or spherical in small crystals on the natural environment. Prismatic on lab grown crystals.
Cleavage	Perfect [010] perfect, [100] distinct, [001] distinct
Mohs scale hardness	2+1⁄2
Luster	Vitreous
Streak	Light yellow
Diaphaneity	Transparent
Specific gravity	2.69
Pleochroism	Visible
Solubility	soluble in water
Other characteristics	Health risks: contains the carcinogenic and mutagenic chromate ion.
References	[2][3]

Lópezite is a rare red chromate mineral with chemical formula: K₂Cr₂O₇. It crystallizes in the triclinic crystal system.^[2][3]

It occurs as rare vug fillings in nitrate ores in association with tarapacáite (K₂CrO₄), dietzeite and ulexite in the Chilean Atacama and is reported from the Bushveld igneous complex of South Africa.^[2][3] Lópezite was first described in 1937 for an occurrence in Iquique Province, Chile and named after Chilean mining engineer Emiliano López Saa (1871–1959).^[2]

Most commercially available lópezite is artificially produced.^[2] Synthetic varieties also exhibit monoclinic crystals.^[4]

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. Lópezite data on Mindat
3. Lópezite data in the Handbook of Mineralogy
4. Richard V. Gaines, H. Catherine W. Skinner, Eugene E. Foord, Brian Mason, and Abraham Rosenzweig: "Dana's new mineralogy", p. 692. John Wiley & Sons, 1997