Star Augite from Vietnam

Le Ngoc Nang, Pham, Minh Tien

Augite is a common and widespread pyroxene mineral that occurs in various rocks (e.g. those of mafic igneous
composition, especially basalt and gabbro). However, it is not known to occur in gem quality. In early 2021,
during field studies of Cenozoic alkaline basalts associated with alluvial sapphires and other gems in Dong Nai Province, southern Vietnam, the authors found several fractured pieces and whole crystals of augite—and most of them displayed a six-rayed star after cutting. Augite has been previously reported as phenocrysts in Cenozoic basalts of southern Vietnam (Hoang & Flower 1998), but according to the authors’ knowledge this is the first time that asterism has been documented in this mineral, notably as pieces large enough for use as gemstones. 

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