Yellow brown crystal aggregates of the rare mineral molysite from Larderello, Pomarance, Pisa Province, Tuscany, Italy. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Molysite
Molysite is an IMA-recognized mineral species in the halide class, with the chemical formula FeCl₃.
It crystallizes in the hexagonal crystal system (space group R-3).
Key properties: specific gravity 2.9; optically uniaxial.
IMA symbol My, grandfathered status — known before the IMA’s founding, named in 1868.
A volcanic sublimate.
It is found associated with Tridymite, hematite, anhydrite, halite (Augustine volcano, Alaska, USA).
Its name comes from the Greek for a stain, as it stains the host rock.
Index entry. This entry combines official IMA/RRUFF species data with published physical-property data — a full written entry hasn’t been published yet.
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