Ferrofettelite

ferrofettelite

proustite

xanthoconite

arsenolite

Images

Formula: [Ag₆As₂S₇][Ag₁₀FeAs₂S₈]
Valence: Ag¹⁺₁₆Fe²⁺As³⁺₄S^2-₁₅
Sulphosalt, sulpharsenite, silver-bearing mineral
Crystal System: Monoclinic
Specific gravity: 5.74 calculated
Streak: Dark reddish grey
Environments

Plutonic igneous environments
Hydrothermal environments

Ferrofettelite is a new mineral, approved in 2021 and to date (January 2026) reported only from the type locality.

Localities

At the type locality, Glasberg quarry, Nieder-Beerbach, Mühltal, Darmstadt-Dieburg, Darmstadt, Hesse, Germany, ferrofettelite occurs as anhedral to subhedral flakes and grains up to 80 μm, associated with proustite and xanthoconite, on arsenolite, calcite and prehnite (MM 86.2.340-345).

Back to Minerals