A dark blue or black mineral of the amphibole group, occurring chiefly in alkaline igneous rocks or as blue asbestos (crocidolite)
- ‘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.’
- ‘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.’
- ‘Glaucophane and riebeckite are found in low-grade schists of basic igneous parentage; crocidolite occurs in medium-grade metamorphosed ironstones.’
- ‘Willman reported astrophyllite, biotite, molybdenite, and riebeckite associated with smoky quartz and microcline (variety amazonite) on Mount Kineo at North Cheyenne Canyon.’
- ‘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.