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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 7–8 on Mohs hardness scale). The cause is speculated as being due to the samples having been riddled with lattice defects and ...
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Musgravite or magnesiotaaffeite-6N’3S is a rare oxide mineral used as a gemstone. Its type locality is the Ernabella Mission, Musgrave Ranges, South Australia, for which it was named following its discovery in 1967. [2] It is a member of the taaffeite family of minerals, [2] [1] and its chemical formula is Be(Mg, Fe, Zn) 2 Al 6 O 12.
Some solid substances that are not minerals have been assigned a hardness on the Mohs scale. Hardness may be difficult to determine, or may be misleading or meaningless, if a material is a mixture of two or more substances; for example, some sources have assigned a Mohs hardness of 6 or 7 to granite but it is a rock made of several minerals ...
The fracture is uneven to conchoidal, the mineral is brittle, and it has hardness 5 + 1 ⁄ 2 to 6, almost as hard as feldspar. All the members of the sodalite group have quite low densities, less than that of quartz ; haüyne is the densest of them all, but still its specific gravity is only 2.44 to 2.50. [ 13 ]
Willemite is a zinc silicate mineral (Zn 2 Si O 4) and a minor ore of zinc.It is highly fluorescent (green) under shortwave ultraviolet light. It occurs in a variety of colors in daylight, in fibrous masses and apple-green gemmy masses.
Chrysoberyl is the third-hardest frequently encountered natural gemstone and lies at 8.5 on the Mohs scale of mineral hardness, between corundum (9) and topaz (8). [ 7 ] An interesting feature of its crystals are the cyclic twins called trillings .
It has a Mohs hardness of 5.0 to 5.5 and a specific gravity of 2.4. It is translucent with a refractive index of 1.50. It is fusible at 3.5 on Wolfgang Franz von Kobell's fusibility scale, and soluble in HCl. It commonly contains or is associated with grains of pyrite.