CRYSTALS

Amethyst  (SiO₂)

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. The ancient Greeks wore amethyst and carved drinking vessels from it in the belief that it would prevent intoxication.

Amethyst is produced in abundance from the state of Minas Gerais in Brazil where it occurs in large geodes within volcanic rocks. Many of the hollow agates of southwestern Brazil and Uruguay contain a crop of amethyst crystals in the interior. Artigas, Uruguay and neighboring Brazilian state Rio Grande do Sul are large world producers exceeding in quantity Minas Gerais, as well as Mato Grosso, Espirito Santo, Bahia, and Ceará states, all amethyst producers of importance in Brazil.

 Vivianite (Fe2+Fe2+2(PO4)2·8H2O) 

 Vivianite is a hydrated iron phosphate mineral found in a number of geological environments.

Pure vivianite is colorless, but the mineral oxidizes very easily, changing the color, and it is usually found as deep blue to deep bluish green prismatic to flattened crystals.

Vivianite crystals are often found inside fossil shells, such as those of bivalves and gastropods, or attached to fossil bone.