Chemistry:Gratonite

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
Strunz classification	2.JB.55
Crystal system	Trigonal
Crystal class	Ditrigonal pyramidal (3m) (same H-M symbol)
Space group	R3m

Gratonite is a lead-arsenic sulfosalt mineral, with the chemical composition Pb₉As₄S₁₅. Gratonite was discovered in 1939 at the Excelsior Mine, Cerro de Pasco, Peru. It is named in honor of geologist L. C. Graton (1880–1970), who had a long-standing association with the Cerro de Pasco mines.

References

• Mineral Data Publishing
• Webmineral
• Mindat