Original paper

Microstructure and origin of colour of chrysoprase from Haneti (Tanzania)

Graetsch, Heribert A.

Abstract

Chrysoprase from Haneti, Tanzania, was investigated by optical reflectance spectroscopy, near infrared absorption spectroscopy and X-ray powder diffraction. Different to chrysoprase from other sources, the green colour is caused by the incorporation of 0.47(6) wt. % gaspeite in the microstructure of microcrystalline quartz.Like other varieties of chalcedony, the microstructure of chrysoprase is characterised by planar lattice faults, a small moganite content, small crystallite size of the quartz domains, microstrain associated with the structural imperfections and a small content of non-essential water. The crystallinity of chrysoprase from Haneti is higher than from many other sources.

Keywords

chrysoprasegaspeitechalcedonymoganitemicrostructure