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Corundum is a crystalline form of aluminium oxide (Al 2 O 3) typically containing traces of iron, titanium, vanadium, and chromium. [ 3 ] [ 4 ] It is a rock -forming mineral . It is a naturally transparent material, but can have different colors depending on the presence of transition metal impurities in its crystalline structure. [ 7 ]
For example, corundum (9) is twice as hard as topaz (8), but diamond (10) is four times as hard as corundum. [citation needed] The table below shows the comparison with the absolute hardness measured by a sclerometer, with images of the reference minerals in the rightmost column. [10] [11]
The Mohs Hardness Scale is the main scale to measure mineral hardness. Finger nail is 2.5, copper coin is 3.5, glass is 5.5 and steel is 6.5. Hardness scale is Talc is 1, Gypsum is 2, Calcite is 3, Fluorite is 4, Apatite is 5, Orthoclase Feldspar is 6, Quartz is 7, Topaz is 8, Corundum is 9 and Diamond is 10. Odor; Not always recommended.
This page was last edited on 16 November 2024, at 12:16 (UTC).; Text is available under the Creative Commons Attribution-ShareAlike 4.0 License; additional terms may apply.
Corundum from Brazil, size about 2×3 cm. The most common form of crystalline aluminium oxide is known as corundum, which is the thermodynamically stable form. [16] The oxygen ions form a nearly hexagonal close-packed structure with the aluminium ions filling two-thirds of the octahedral interstices. Each Al 3+ center is octahedral.
Because of white fused alumina's hardness (9.0 on the Mohs scale), It is second only to diamond and silicon carbide.It is commonly used as a raw material in abrasive tools, blasting, lapping, polishing, and grinding. white fused alumina is also used in refractories and ceramic shapes laminates due to chemical stability, high melting point, etc.
Sapphires are a color variety of corundum, a crystalline form of aluminium oxide (Al 2 O 3). [14] Corundum is one of the hardest minerals, rating 9 on the Mohs scale. [15] Corundum gems of most colors are called sapphires, except for red ones, which are called rubies. [16] The term "Yogo sapphire" refers only to sapphires from the Yogo Gulch. [17]
Adamantine spar is a silky brown variety of corundum. It has a hardness of 9 on the Mohs scale. [1] See also. Yogo sapphire; References This page was last edited ...