gems, jade, pyroxene jade, jadeite, fei cui, omphacite, kosmochlor, Guatemala, geology

Jadeite occurs as inclusions in serpentinite in the Motagua fault zone. A boulder of remarkable size and purity was found near Manzanal, Guatemala, and chemical, optical, and X-ray studies have been made of a separated sample of the jadeite. Elsewhere in the Motagua fault zone, omphacite-garnet eclogites and glaucophane-lawsonite-omphacite-garnet rocks have been found in similar environments. Only at the Manzanal locality, however, have sodic pyroxenes been found in rocks which are nearly monomineralic.