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
Shelby Gem Factory some of the company's products are "simulants" (such as their diamond simulants), their synthetic ruby and sapphire stones are not imitations – they have the same chemical and crystalline structure that is found in natural stones. The factory's FAQ says "our rubies and sapphires are really ruby and sapphire!" The Shelby Gem Factory also manufactures simulated citrine and topaz, along with other birthstone substitutes. As per the company website's FAQ section in 2017, below are the Mohs scale hardness values for some well-known gems along with Shelby gem products: The company's policy is to maintain the confidentiality of celebrity clients,