File:Corundum (Soutpansberg Range area, South Africa) 1.jpg

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English: A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 5700 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.

The oxide minerals all contain one or more oxide anions (O-2). The oxide minerals include species that are hydroxy-oxides. The hydroxide minerals (those with one or more OH-) are usually considered together with the oxides. Many sulfide minerals are not stable in Earth-surface conditions. In the presence of oxygen and moisture, sulfide minerals tend to tarnish or alter to oxides and hydroxy-oxides. All except the most inert elements (such as the platinum-group elements and gold and noble gases) readily form oxides. Gold oxide forms only under special conditions.

Corundum is aluminum oxide - Al2O3. At H≡9, it is the hardest common mineral, apart from diamond. Corundum forms hexagonal crystals, which is evident even in many river-worn specimens. The hexagonal columns of corundum typically have well-developed flat tops & bottoms. These flat ends are not cleavage planes - corundum has no cleavage. The cleavage-looking flat tops & bottoms of corundum are called partings (pseudocleavage). Additional breakages will not be along planar surfaces.

The color of corundum is variable - it can be any color, including plaid patterns. If transparent and relatively fracture-free & inclusion-free, corundum is said to be of gem-quality, and the color determines the name of the gem.

deep red = ruby blue = sapphire pale red = sapphire pale green = sapphire purple = sapphire yellow = sapphire

Locality: unrecorded / undisclosed site in the Soutpansberg Range area, Vhembe District, Limpopo Province, northeastern South Africa


Photo gallery of corundum:

www.mindat.org/gallery.php?min=1136
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Source https://www.flickr.com/photos/47445767@N05/52018532742/
Author James St. John

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This file is licensed under the Creative Commons Attribution 2.0 Generic license.
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/52018532742. It was reviewed on 21 April 2022 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0.

21 April 2022

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current14:17, 21 April 2022Thumbnail for version as of 14:17, 21 April 20223,191 × 2,512 (4.65 MB)Ser Amantio di Nicolao (talk | contribs)Uploaded a work by James St. John from https://www.flickr.com/photos/47445767@N05/52018532742/ with UploadWizard

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