Walfordite

Walfordite is a very rare tellurite mineral that was discovered in Chile in 1999.[4] The mineral is described as orange with orange-yellow streak, and is determined to have a chemical formula of Fe³⁺,Te⁶⁺Te⁴⁺₃O₈[1] with minor titanium and magnesium substitution resulting in an approximate empirical formula of (Fe³⁺,Te⁶⁺,Ti⁴⁺,Mg)(Te⁴⁺)₃O₈.[4]

Walfordite (0.7 mm) in alunite, Tambo Mine

Walfordite
Walfordite from Tambo Mine, Elqui Province, Chile
General
Category	Tellurite minerals
Formula (repeating unit)	Fe^3+,Te^6+Te^4+3O8
Strunz classification	4.JK.05
Crystal system	Isometric
Space group	I2, Ia3
Unit cell	a = 11.011 Å ; Z = 8
Identification
Colour	Orange
Crystal habit	Microscopic cubic crystals
Cleavage	None
Tenacity	Brittle
Luster	Adamantine
Streak	Orange-yellow
Diaphaneity	Opaque
Specific gravity	5.841 (calculated)
Optical properties	Isotropic
Refractive index	n = 2.23
References	[1][2][3]

Occurrence

The only reported occurrence[2] is in the Wendy open pit, El Indio-Tambo mining district of the Coquimbo Region, northern Chile where it occurs in oxidized breccia associated with a tellurium-bearing gold deposit. Associated minerals include: alunite, rodalquilarite, native gold, emmonsite, jarosite and pyrite. The mineral was named for mine geologist Phillip Walford (1945— ) who first noted the mineral.[1]

See also

• El Indio Gold Belt. Tambo is adjacent to the El Indio mine. Both are now closed.

References

1. Walfordite in the Handbook of Mineralogy
2. Walfordite on Mindat.org
3. Walfordite data on Webmineral
4. Back, Malcolm E.; Grice, Joel D.; Gault, Robert A.; Criddle, Alan J.; Mandarino, Joseph A. (1999). "Walfordite, a New Tellurite Species from the Wendy Open Pit, El Indio - Tambo Mining Property, Chile" (PDF). The Canadian Mineralogist. 37: 1261–1268.