AMASONITE

Description:

Amazonite (sometimes called "Amazon stone") is a green variety of microcline feldspar. Its colour varies from bright verdigris green to a bluish green. The name Amasonite is taken from that of the Amazon River, from which certain green stones were formerly obtained, but it is doubtful whether green feldspar occurs in the Amazon area. Amazonite is the best known variety of feldspar which has been  used in jewellery for quite a long time.

Amazonite is a mineral of limited occurrence. Formerly it was obtained almost exclusively from the area of Miyask in the Ilmen mountains, 50 miles southwest of Chelyabinsk, Russia, where it occurs in granitic rocks. More recently, high-quality crystals have been obtained from Pikes Peak, Colorado, where it is found associated with smoky quartz, orthoclase and albite in a coarse granite or pegmatite. It is also found in pegmatite in Madagascar.

Because of its bright green colour when polished, amazonite is cut and used in jewellery. For many years, the source of amazonite's color was a mystery. Naturally, many people assumed the color was due to copper because copper compounds often have blue and green colors. More recent studies suggest that the blue-green color is due to small quantities of lead and water in the feldspar.

Amazonite has been mined in Minas Gerais (Brazil), Colorado (U.S.) and the Ural Mountains of Russia.

Characteristics:

• Chemistry: KAlSi₃O₈
• Class: tektosilicate
• Hardness (Mohs scale) : 6 – 6.5
• Density: 2.54-2.63
• Refractive index: 1.53
• Dispersion: 0.012
• Crystal system: triclinic
• Crystal habit: as anhedral to euhedral crystals or massive, lattice (perthitic) intergrowth with albite is usually present, also rarely in a cuneform interpenetrating pattern with quartz known as graphic granite
• Luster: vitreous
• Transparency: opaque to translucent, rarely transparent
• Cleavage: characteristic cleavages are perfect and distinct intersecting at approximately ninety degrees