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The Logan Sapphire brooch, National Museum of Natural History, Washington, D.C. The Logan Sapphire is a 422.98-carat (84.596 g) sapphire from Sri Lanka.One of the largest blue faceted sapphires in the world, it was owned by Victor Sassoon and then purchased by M. Robert Guggenheim as a gift for his wife, Rebecca Pollard Guggenheim, who donated the sapphire to the Smithsonian Institution in 1960.
The 423-carat (85 g) blue Logan Sapphire. Sapphire is a saturated shade of blue, referring to the gemstone of the same name. Sapphire gems most commonly occur in a range of blue shades, although they can come in many different colors. Other names for variations of the color sapphire are blue sapphire or sapphire blue, shown below.
In October 2014, Sotheby's Hong Kong achieved consecutive per-carat price records for Kashmir sapphires – first with the 12.00 carat Cartier sapphire ring at US$193,975 per carat, then with a 17.16 carat sapphire at US$236,404, and again in June 2015 when the per-carat auction record was set at US$240,205. [39]
Quartz is, therefore, classified structurally as a framework silicate mineral and compositionally as an oxide mineral. Quartz is the second most abundant mineral in Earth's continental crust, behind feldspar. [10] Quartz exists in two forms, the normal α-quartz and the high-temperature β-quartz, both of which are chiral. The transformation ...
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]
Quartzite can have a grainy, glassy, sandpaper-like surface. Quartzite is a hard, non-foliated metamorphic rock which was originally pure quartz sandstone. [1] [2] Sandstone is converted into quartzite through heating and pressure usually related to tectonic compression within orogenic belts.