Phrehnite

Phrehnite

Prehnite is an inosilicate with the formula Ca2Al(AlSi3O10)(OH)2  It is a hydrothermal mineral, filling cavities in basaltic volcanic rocks, and also lining fractures in various intrusive and metamorphic rocks. The specimen is from Loanhead quarry, Nr. Beith in Scotland, and is a botryoidal aggregate with no crystals observed. part of the surface is peppered with small calcite "rosettes" with a slightly orange colouration. Prehnite of suitable quality is much used in jewellery.