Agmantinite

agmantinite

wurtzite

alabandite

manganoquadratite

Images

Formula: Ag₂MnSnS₄
Valence: Ag¹⁺₂Mn²⁺Sn⁴⁺S^2-₄
Sulphide of silver, manganese and tin
Crystal System: Orthorhombic
Specific gravity: 4.574 calculated for the empirical formula
Hardness: 2 to 2½
Streak: Red
Colour: Orange-red
Environments

Hydrothermal environments

Agmantinite was approved in 2014 but to date (Movember 2025) it has been reported only from the type locality.

Localities

At the type locality, the Uchucchacua Mine, Uchucchacua area, Oyón District, Oyón Province, Lima, Peru, agmantinite occurs as translucent, orange–red crystals up to 100 μm across, with an adamantine lustre. It is the first known mineral of M^IIM^IVS₄ type that is derived from wurtzite rather than sphalerite by ordered substitution of Zn, analogous to the substitution pattern for deriving stannite from sphalerite (MM 83.2.233-238).
Agmantinite occurs in the alabandite zone of the polymetallic hydrothermal mineral deposit, associated with calcite, quartz, manganoquadratite, alabandite, proustite, probable kutnohorite, sphalerite and Pb-Sb-As-S minerals (HOM).
Agmantinite from the Uchucchacua Mine - Image

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