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  2. Corundum - Wikipedia

    en.wikipedia.org/wiki/Corundum

    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 ]

  3. Corundum (structure) - Wikipedia

    en.wikipedia.org/wiki/Corundum_(structure)

    Corundum is the name for a structure prototype in inorganic solids, derived from the namesake polymorph of aluminum oxide (α-Al 2 O 3). [1] Other compounds, especially among the inorganic solids, exist in corundum structure, either in ambient or other conditions.

  4. Aluminium oxide - Wikipedia

    en.wikipedia.org/wiki/Aluminium_oxide

    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.

  5. Sapphire - Wikipedia

    en.wikipedia.org/wiki/Sapphire

    Sapphire is one of the two gem-varieties of corundum, the other being ruby (defined as corundum in a shade of red). Although blue is the best-known sapphire color, it occurs in other colors, including gray and black, and also can be colorless. A pinkish orange variety of sapphire is called padparadscha.

  6. Ruby - Wikipedia

    en.wikipedia.org/wiki/Ruby

    Ruby is a pinkish red to blood-red colored gemstone, a variety of the mineral corundum (aluminium oxide). Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called sapphires. Ruby is one of the traditional cardinal gems, alongside amethyst, sapphire, emerald, and diamond. [3]

  7. Portal:Minerals - Wikipedia

    en.wikipedia.org/wiki/Portal:Minerals

    The name "corundum" is derived from the Tamil-Dravidian word kurundam (ruby-sapphire) (appearing in Sanskrit as kuruvinda). Because of corundum's hardness (pure corundum is defined to have 9.0 on the Mohs scale ), it can scratch almost all other minerals.

  8. Aluminium compounds - Wikipedia

    en.wikipedia.org/wiki/Aluminium_compounds

    Aluminium forms one stable oxide with the chemical formula Al 2 O 3, commonly called alumina. [15] It can be found in nature in the mineral corundum, α-alumina; [16] there is also a γ-alumina phase. [13]

  9. Spinel - Wikipedia

    en.wikipedia.org/wiki/Spinel

    After the 18th century, the word ruby was only used for the red gem variety of the mineral corundum, and the word spinel came to be used. [16] " Balas" is derived from Balascia, the ancient name for Badakhshan , a region in central Asia situated in the upper valley of the Panj River , one of the principal tributaries of the Oxus River .