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Science 1 July 1966:
Vol. 153. no. 3731, pp. 60 - 62
DOI: 10.1126/science.153.3731.60
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Articles

Cohenite in Meteorites: A Proposed Origin

Robin Brett 1

1 U. S. Geological Survey, Washington, D. C. 20242

Cohenite [(Fe, Ni)3C] is found almost exclusively in meteorites containing from 6 to 8 percent nickel (by weight). On the basis of iron-nickel-carbon phase diagrams at 1 atmosphere and of kinetic data, the occurrence of cohenite within this narrow composition range as a low-pressure metastable phase and the nonoccurrence of cohenite in meteorites outside the range 6 to 8 percent nickel can be explained. Cohenite formed in meteorites containing less than 6 to 8 percent nickel decomposed to metal and graphite during cooling; it cannot form in meteorites containing more than about 8 percent. The presence of cohenite in meteorites cannot be used as an indicator of pressure of formation. However, the absence of cohenite in meteorites containing the assemblage, metal plus graphite, requires low pressures during cooling.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Cliftonite in Meteorites: A Proposed Origin.
R. Brett, R. Brett, and G. T. Higgins (1967)
Science 156, 819-820
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Science. ISSN 0036-8075 (print), 1095-9203 (online)