bjones
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Two natural substances have recently been tested as being harder than diamonds: wurtzite boron nitride and lonsdaleite. However, these minerals are so rare that it is difficult to obtain enough for testing let alone for it to be used in any practical applications.
Between 2009 and 2010, scientists conducted a series of tests on two rare minerals known as wurtzite boron nitride and lonsdaleite. Wurtzite boron nitride (W-bn) has a structure that is very similar to that of diamond, but it is not composed of carbon atoms like a diamond. In testing, W-bn has proven to be 18 percent harder than diamond. However, these tests were only computer simulations. It is estimated the actual strength of the material will prove far harder in actual physical testing.
The second material, lonsdaleite, is also known as hexagonal diamond. Lonsdaleite is made of carbon atoms, but they are arranged differently than the atoms of a diamond. In simulations, it has proven to be 58 percent harder than diamond.
The reason why physical testing is so slow to be done is because of the extreme rarity of both of these minerals. W-bn is formed during some volcanic eruptions involving high pressure and high temperature, while lonsdaleite is found naturally only in certain meteorites with a high graphite content.
Although W-bn is not the stronger of the two, scientists are giving it more attention because of its stability in oxygen-rich environments. This would make it perfect for use a cutting or drilling tool. Scientists have discovered that its strength is, paradoxically, due to the flexibility of the bonds between the atoms of which it is composed. When put under stress, the bonds can actually bend and then realign by 90 degrees into new bonds that can be up to 80 percent stronger than the previous bonds.
 Posted 4531 day ago
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