Gratonite

Not to be confused with Graftonite.

Gratonite is a lead-arsenic sulfosalt mineral, with the chemical composition Pb₉As₄S₁₅. It is considered a low-temperature dimorph of jordanite. Gratonite was discovered in 1939 at the Excelsior Mine, Cerro de Pasco, Peru. ^[2] It is named in honor of geologist L. C. Graton (1880–1970), who had a long-standing association with the Cerro de Pasco mines. The other location where it is found is the Riotinto mine, Minas de Riotinto (Huelva), Spain. The crystals are very similar to those from Cerro de Pasco.^[3]

Gratonite
Gratonite, Excelsior Mine, Cerro de Pasco, Peru, the type locality. 1.7 x 1.6 x 1.5 cm.
General
Category	Sulfosalt minerals
Formula (repeating unit)	Pb9As4S15
IMA symbol	Gtn[1]
Strunz classification	2.JB.55
Crystal system	Trigonal
Crystal class	Ditrigonal pyramidal (3m) (same H-M symbol)
Space group	R3m

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. Palache, C. and Fisher, D.J. (1940). "Gratonite - A new mineral from Cerro de Pasco". American Mineralogist. 25: 255–265.{{cite journal}}: CS1 maint: multiple names: authors list (link)
3. Calvo Rebollar, Miguel (2003). Minerales y Minas de España. Vol. II. Sulfuros y sulfosales [Minerals and mines of Spain] (in Spanish). Vitoria, Spain: Museo de Ciencias Naturales de Alava. pp. 590–591. ISBN 978-84-7821-543-0.

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