Amethyst cushion-cut gemstone

Description

Amethyst isa 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. Ancient Greeks wore amethyst and carved drinking vessels from it in the belief that it would prevent intoxication.

Amethyst, a semi-precious stone, is often used in jewelry.  Amethyst is a purple variety of quartz (SiO₂) and owes its violet color to irradiation, impurities of iron (Fe3+) and in some cases other transition metals, and the presence of other trace elements, which result in complex crystal lattice substitutions.  The irradiation causes the iron  atoms that replace Si in the lattice to lose an electron and form a [FeO₄]⁰ color.   Amethyst is a three-dimensional network of tetrahedra where the silicon atoms are in the center and are surrounded by four oxygen atoms located at the vertices of a tetrahedron. This structure is quite rigid and results in quartz’s hardness and resistance to weathering. The hardness of the mineral is the same as quartz, thus making it suitable for use in jewelry.