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Formula (repeating unit) Silica (silicon dioxide, ... Amethyst is a violet variety of quartz. ... it was considered a symbol of royalty and used to decorate English ...
Formula (repeating unit) SiO 2: IMA symbol: Qz [2] Strunz classification: 4 ... Russia, France, Namibia, and Morocco. Amethyst derives its color from traces of iron ...
Amesite is a mineral with general formula of Mg 2 Al 2 SiO 5 (OH) 4. [3] Amesite crystallizes in the triclinic crystal system. [5] It contains three axes of unequal length, not at right angles. It was first described in 1876 for an occurrence in the Chester Emery Mines, Chester, Hampden County, Massachusetts. It was named for mine owner James Ames.
Amethyst loses its natural violet color when heated to above 200-300°C and turns a color that resembles natural citrine, but is often more reddish or brownish. [9] Unlike natural citrine, the color of heat-treated amethyst is known to come exclusively from trace amounts of iron oxides, specifically hematite and goethite .
The chemical composition which was given by Tschermak in 1884 for this dravite approximately corresponds to the formula NaMg 3 (Al,Mg) 6 B 3 Si 6 O 27 (OH), which is in good agreement (except for the OH content) with the endmember formula of dravite as known today. [9] Dravite varieties include the deep green chromium dravite and the vanadium ...
Charoite (/ tʃ æ r oʊ. aɪ t / CHAR-ow-ait) is a rare silicate mineral with the chemical composition K(Ca,Na) 2 Si 4 O 10 (OH,F)•H 2 O, first described in 1978.It is named after the Chara River, despite its being 70 kilometres (43 mi) away from the discovery place.
Rhodonite is a manganese inosilicate, with the formula (Mn, Fe, Mg, Ca)SiO 3, and member of the pyroxenoid group of minerals, crystallizing in the triclinic system. It commonly occurs as cleavable to compact masses with a rose-red color (its name comes from Ancient Greek ῥόδον (rhódon) 'rose'), often tending to brown due to surface oxidation.
Seifertite is a silicate mineral with the formula SiO 2 and is one of the densest polymorphs of silica.It has only been found in Martian [4] [5] and lunar meteorites, [6] where it is presumably formed from either tridymite or cristobalite – other polymorphs of quartz – as a result of heating during the atmospheric entry and impact to the Earth, at an estimated minimal pressure of 35 GPa.