Feature
Gems & Gemology, Summer 1996, Vol. 32, No. 2
Opal from the Shewa Province, Ethiopia
Mary L. Johnson, Robert C. Kammerling, と Dino G. DeGhionno, and John I. Koivula
Opal occurs as nodules in volcanic rocks at a new gem opal locality in the Menz Gishe district of Shewa Province, Ethiopia. The opal field, still in the early stages of exploration, extends over several square kilometers. Opals from Shewa Province have near-colorless to white, yellow, orange, gray, or brown body colors; some show face-up play-of-color, and many have contra luz play-of-color. The gemological properties are consistent with those of other natural opals, and small particles are common inclusions. Preliminary stability tests indicate that much of the material absorbs water and some crazes when exposed to light and heat.
