Euclase

Euclase is a beryllium aluminium hydroxide silicate mineral (BeAlSiO₄(OH)). It crystallizes in the monoclinic crystal system and is typically massive to fibrous as well as in slender prismatic crystals. It is related to beryl (Be₃Al₂Si₆O₁₈) and other beryllium minerals. It is a product of the decomposition of beryl in pegmatites.