Crocidolite from the Koegas-Westerberg area, South Africa

Contains sections dealing with the occurrence of the asbestos, by Cilliers, and with results of mineralogic investigations, by A. G. Freeman, A. Hodgson, and H. F. W. Taylor. The crocidolite (fibrous riebeckite) seams occur at three main horizons in Precambrian banded ironstones (lower Griquatown stage of the Pretoria series) consisting of alternating thin layers of chert, stilpnomelane, minnesotaite, riebeckite, carbonates and (rarely) magnetite, folded and intruded in places by basic sills. X-ray, chemical, differential thermal, and other analyses show little difference in the composition and properties of crocidolite from weathered and unweathered zones, although the weathered material has a slightly higher ratio of ferric to ferrous iron.

This record provided courtesy of AGI/GeoRef.