Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
There are a couple threads on Linkedin referring to the mineral Lonsdaleite. Although the premise of the threads was that Lonsdaleite was harder than diamond, that does not appear to be the case unless it is made synthetically.
But, how it occurs naturally is astoundingly interesting.
Lonsdaleite (named in honor of Kathleen Lonsdale), is an allotrope of carbon with an hexagonal xl structure. It forms when meteorites containing graphite strike the Earth. The great heat and stress of the impact transforms the graphite into diamond, but retains graphite's hexagonal crystal lattice. Lonsdaleite was first identified in 1967 from the Canyon Diablo meteorite, where it occurred as microscopic crystals associated with diamond.
The hardness of Lonsdaleite is recorded as being 7-8 on Mohs Scale, as a result of it being heavily included with impurities.
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