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
Weeksite Weeksite Weeksite is a naturally occurring uranium silicate mineral with the chemical formula: K(UO)SiO•4(HO), potassium uranyl silicate. Weeksite has a Mohs hardness of 1-2. It was named for USGS mineralogist Alice Mary Dowse Weeks (1909–1988). Weeksite is visually similar to other uranium minerals such as carnotite and zippeite, both being encrustations that form on other rocks (usually sandstones or limestones). Weeksite was first described in 1960 for an occurrence on Topaz Mountain, Thomas Range, Juab County, Utah. Weeksite occurs within small "opal" veins within rhyolite and agglomerates, and as encrustations in sandstones and limestones. It occurs associated with opal, chalcedony,