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Mohs scale hardness: 7.5–8.0: Luster: Vitreous: Streak: White: Diaphaneity: Transparent to opaque: Specific gravity (Depending on the composition) The rare Zn-rich spinel can be as high as 4.40, otherwise it averages from 3.58 to 3.61. Optical properties: Isotropic: Refractive index: 1.719: Pleochroism: Absent: Solubility: None: Other ...
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 ...
Mohs scale of mineral hardness; Mohs hardness of materials (data page) Vickers hardness test; Brinell scale This page was last edited on ...
Mohs scale hardness: 7.5: Luster: Vitreous (glassy) Streak: ... Hercynite is a spinel mineral with the formula FeAl 2 O 4. ... Due to its hardness it also is found in ...
Because it can be a mixture of minerals, no definite Mohs hardness can be assigned: the hardness of corundum is 9 and that of some spinel-group minerals is near 8, but the hardness of others such as magnetite is near 6.
Most pieces of the gem, prior to Taaffe, had been misidentified as spinel. For many years afterwards, it was known only in a few samples, and it is still one of the rarest gemstone minerals in the world. [6] Since 2002, the International Mineralogical Association-approved name for taaffeite as a mineral is magnesiotaaffeite-2N'2S.
Galaxite, also known as 'mangan-spinel' is an isometric mineral belonging to the spinel group of oxides with the ideal chemical formula Mn 2+ Al 2 O 4. [5] It is sometimes used as a gemstone. [ 6 ]
Nichromite (Ni,Co,Fe)(Cr,Fe,Al) 2 O 4 [1] is a black cubic metallic mineral and member of the spinel group. [5] Nichromite was originally reported from the Bon Accord nickel deposit in Barberton District, South Africa. [1] Occurring naturally in a nickel deposit, nichromite is named for chromite with dominant nickel. [2]