Brucite


Composition: Mg(OH)2
Crystal System : Trigonal
Colours: White, off-white
Lustre : Vitreous, waxy, pearly
Hardness (H) : 2.5-3.0
Specific Gravity (S.G) : 2.39
References: Belendorff (2006)

Distribution

Extremely rare, (but easily overlooked).

Occurrence

  • Supergene

Paragenetic and General Notes

Brucite was first recognised at Tsumeb by Bellendorff (2006) on a specimen from "an old German collection".  It occurs as dull-white tabular crystals arranged in rosette-like aggregates, and as earthy crusts (with sepiolite), as part of an unusual paragenesis with the following sequence: 

Cerussite (with hydrocerussite) >> wulfenite >> dolomite >> parkinsonite >> calcite (rhombohedral) >> brucite (with sepiolite) >> calcite (scalenohedral).  

Notably, parkinsonite (a rare lead-molybdenum oxychloride) was also first identified from Tsumeb from this same specimen.