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Amethyst is a violet variety of quartz.The name comes from the Koine Greek αμέθυστος amethystos from α - a-, "not" and μεθύσκω (Ancient Greek) methysko / μεθώ metho (Modern Greek), "intoxicate", a reference to the belief that the stone protected its owner from drunkenness. [1]
unit cell Unit cell dimensions and number (Z) of formula units per unit cell: molweight molar mass of the chemical formula above: color common colors of the mineral: colour same as above, but for British pages: habit common mineral habit: system crystal system (cubic, etc.) class crystal class: twinning common type of twinning: cleavage type of ...
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 .
Taaffeite (/ ˈ t ɑː f aɪ t /; BeMgAl 4 O 8) is a mineral, named after its discoverer Richard Taaffe (1898–1967) who found the first sample, a cut and polished gem, in October 1945 in a jeweler's shop in Dublin, Ireland.
Lepidolite is a lilac-gray or rose-colored member of the mica group of minerals with chemical formula K(Li,Al) 3 (Al,Si,Rb) 4 O 10 (F,OH) 2. [2] [3] It is the most abundant lithium-bearing mineral [4] and is a secondary source of this metal. It is the major source of the alkali metal rubidium.
Although the unit cell is close to being hexagonal in shape ("a" and "c" are nearly equal and β nearly 120°), it is inherently monoclinic and cannot be hexagonal. The crystal structure of coesite is similar to that of feldspar and consists of four silicon dioxide tetrahedra arranged in Si 4 O 8 and Si 8 O 16 rings.
Analcime crystals always look pseudocubic. [3] Its common crystal forms include trapezohedron, truncated trapezohedron with cubic faces, and more rarely either as a truncated trapezohedron, or the crystals can take the shape of a truncated cube that is typical to bixbyites. [4]