Occurrence and Formation of Natural Diamond

The two major allotropes of the element carbon, graphite and diamond, occur in igneous rocks.Pl As seen in Ch. 11, at ordinary pressures 

Source of Carbon In Igneous Rocks. The source of carbon in igneous rocks is still controversi2d. It could be an original constituent in materials deep in the crust or mantle, or it could be organic materials from partially-melted sedimentary rocks or carbonates. 

Diamond Minerals. The mineral k/mber//te is so far the major source of natural diamond. New information and new studies in progress, particularly in Russia, may add evidence of additional origins for diamond besides kimberlite magma.P]WI J 

Interstellar Diamond. Diamond has also been found in meteorites and has been detected in dust generated by supernovas and red giants (see Ch. 11, Sec. 2.5). 

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