The Hardest Substance On Earth

发帖者 ADuu | 2/26/2009 01:37:00 PM | , , , | 0 评论 »

What is the hardest substance on Earth?Diamond?NO,scientists tell you:No!Diamond is always a woman’s best friend!But it is no longer the hardest substance in the world. According to scientists,a called lonsdaleite,which scientists have discovered is 58% harder,and lonsdaleite's a little trickier to acquire.

From wikipedia:Lonsdaleite (named in honour of Kathleen Lonsdale), also called Hexagonal diamond in reference to the crystal structure, is an allotrope of carbon with a hexagonal lattice. In Nature, it forms from graphite present in meteorites upon their impact to 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 from the Canyon Diablo meteorite at Barringer Crater (also known as Meteor Crater) in Arizona. It was first discovered in 1967. Lonsdaleite occurs as microscopic crystals associated with diamond in the Canyon Diablo meteorite; Kenna meteorite, New Mexico; and Allan Hills (ALH) 77283, Victoria Land, Antarctica meteorite. It has also been reported from the Tunguska impact site, Russia.

Hexagonal diamond has also been synthesized in the lab, perhaps even earlier than 1967, by compressing and heating graphite either in a static press or using explosives.

It is translucent brownish-yellow in color and has an index of refraction from 2.40 to 2.41, a specific gravity from 3.2 to 3.3, and a Mohs hardness of 7–8 (11). The Mohs hardness of diamond is 10; the lower hardness of lonsdaleite is chiefly attributed to impurities and imperfections in the naturally occurring material, and a pure sample could be 58% harder than diamond.[1] It can also be created by the thermal decomposition of a polymer, poly (hydridocarbyne), at atmospheric pressure under argon starting at 110 °C (230 °F).
via itv news

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