A dark blue or black mineral of the amphibole group, occurring chiefly in alkaline igneous rocks or as blue asbestos (crocidolite).‘Willman reported astrophyllite, biotite, molybdenite, and riebeckite associated with smoky quartz and microcline (variety amazonite) on Mount Kineo at North Cheyenne Canyon.’
- ‘Later in the week we enticed the government guys to take us to a locality called Kent, quite a drive from Karaganda, where in a beautiful setting we collected fluorite, riebeckite, and zircon from granite.’
- ‘Glaucophane and riebeckite are found in low-grade schists of basic igneous parentage; crocidolite occurs in medium-grade metamorphosed ironstones.’
- ‘The mineral is found as small pink to gray masses of microcrystals in quartz-feldspar pegmatites and veins in association with astrophyllite, riebeckite, and zircon.’
- ‘On the other hand, there is evidence that long-term exposure to asbestiform riebeckite can be dangerous.’
Late 19th century from the name of Emil Riebeck (died 1885), German explorer, + -ite.
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