Walfordite

Walfordite
Walfordite from Tambo Mine, Elqui Province, Chile
General
Category	Tellurite minerals
Formula	Fe3+,Te6+Te4+3O8
IMA symbol	wfd [1]
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	[2] [3] [4]

Walfordite is a very rare tellurite mineral that was discovered in Chile in 1999. ^[5] The mineral is described as orange with orange-yellow streak, and is determined to have a chemical formula of Fe³⁺,Te⁶⁺Te⁴⁺₃O₈ ^[2] with minor titanium and magnesium substitution resulting in an approximate empirical formula of (Fe³⁺,Te⁶⁺,Ti⁴⁺,Mg)(Te⁴⁺)₃O₈. ^[5]

Occurrence

The only reported occurrence ^[3] 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. ^[2]

See also

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

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. Walfordite in the Handbook of Mineralogy
3. Walfordite on Mindat.org
4. Walfordite data on Webmineral
5. 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.