Crystal System: Trigonal
Status of Occurrence: Confirmed Occurrence
Distribution: Locally Abundant
Chemical Composition: Magnesium hydroxide
Chemical Formula: Mg(OH)2
Method(s) of Verification: Holy Island - polarizing-light microscopy (Greenly, 1919).
Introduction: brucite is a white mineral when pure but may be greenish or brown when it contains impurities such as iron (as Fe2+) or manganese. It typically forms by the alteration of periclase (MgO) found metamorphosed dolomites and magnesian limestones metamorphosed at high tempertaures. It is also found as a low-temperature hydrothermal mineral in magnesium-rich rocks such as sepentinites or chlorite schists.
Occurrence in Wales: the only recording of brucite in Wales is by Greenly (1919) who described its presence in talc schist exposed on Holy Island, Anglesey.

Key Localities:

  • Holy Island, Anglesey: Greenly (1919) recorded bright green scales in talc schist derived from the alteration (serpentinization) of ultrabasic rocks exposed on the small islet in Rhyd-y-Bont Creek. No further data on this occurrence is currently available.

There are no key localities for this specimen.


  1. Greenly, E., 1919. The Geology of Anglesey. Memoirs of the Geological Survey of Great Britain, 980pp (2 volumes).

There are no references for this specimen.