Alpersite

alpersite

pickeringite

alunogen

epsomite

Images

Formula: Mg(SO4).7H2O
Hydrated sulphate, melanterite group
Specific gravity:
Hardness: 2½
Streak: White
Colour: Blue, pale blue, whitish
Common impurities: Cu,Zn,Mn,Fe
Environments

Hydrothermal environments

Alpersite is an efflorescent secondary mineral, likely widespread and unnoticed in mine wastes that contain copper-bearing sulphides, but in which solubilised Fe2+ is not available for melanterite crystallisation because of oxidation to Fe3+ in surface waters of near-neutral pH. Associated minerals include pickeringite, alunogen, epsomite and gypsum (HOM).

Localities

At the type locality, the Big Mike mine, Tobin and Sonoma Range Mining District, Pershing county, Nevada, USA, alpersite, a mineral species with direct relevance to reactions in mine waste, occurs in a mineralogically zoned assemblage in sheltered areas at the abandoned Big Mike mine, at a relative humidity of 65% and temperature 4oC. Blue alpersite, which is isostructural with melanterite, is overlain by a light blue to white layer dominated by pickeringite, alunogen and epsomite. It is suspected that alpersite and copper-bearing pentahydrite are widespread in mine wastes that contain copper-bearing sulphides, but in which solubilised Fe2+ is not available for melanterite crystallisation because of oxidation to Fe3+ in surface waters of near-neutral pH (AM 91.261-269).

Back to Minerals