Lonsdaleite static press or using explosives. It has also been produced by chemical vapor deposition, and also by the thermal decomposition of a polymer, poly(hydridocarbyne), at atmospheric pressure, under argon atmosphere, at . It is translucent, brownish-yellow, and has an index of refraction of 2.40 to 2.41 and a specific gravity of 3.2 to 3.3. Its hardness is theoretically superior to that of cubic diamond (up to 58% more), according to computational simulations, but natural specimens exhibited somewhat lower hardness through a large range of values (from 7 to 8 on Mohs hardness scale). The cause is speculated as being due
Brinell scale Brinell scale The Brinell scale characterizes the indentation hardness of materials through the scale of penetration of an indenter, loaded on a material test-piece. It is one of several definitions of hardness in materials science. Proposed by Swedish engineer Johan August Brinell in 1900, it was the first widely used and standardised hardness test in engineering and metallurgy. The large size of indentation and possible damage to test-piece limits its usefulness. However it also had the useful feature that the hardness value divided by two gave the approximate UTS in ksi for steels. This feature contributed to its early adoption