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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 ]
When A is nonmetallic and B is metallic, the structure becomes the antiphase of corundum, called the anticorundum structure type, [8] with examples including β-Ca 3 N 2 [9] and borates. Ternary and multinary compounds can also exists in the corundum structure. The corundum-like structure with the composition A 2 BB'O 6 is called double ...
The government of the Socialist Republic of Vietnam maintains that between 2 September 1945 and 2 July 1976 only the Democratic Republic of Vietnam and the Republic of South Vietnam were legitimate governments and that any rival governments were illegal ("reactionary" or "counter-revolutionary") organisations.
Download as PDF; Printable version; In other projects Wikidata item; ... Adamantine spar is a silky brown variety of corundum. It has a hardness of 9 on the Mohs ...
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The Vietnamese Wikipedia initially went online in November 2002, with a front page and an article about the Internet Society.The project received little attention and did not begin to receive significant contributions until it was "restarted" in October 2003 [3] and the newer, Unicode-capable MediaWiki software was installed soon after.
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