Geographic Minerals

Amazonite: Properties and Occurrence

Amazonite: Properties and Occurrence

Amazonite (sometimes called “Amazon stone”) is a green variety of microcline feldspar. Is translucent to opaque feldspar gemstone with a pretty green color. It is the greenish variety of the mineral Microcline.

Amazonite is named after the Amazon River of South America. The name 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. There are no Amazonite deposits that exist in the Amazon region, so presumably, this stone is named to its resemblance in color to the green of the tropical rainforest.

General Information

  • Color: Green, Blue, Grey, Purple
  • Luster: Vitreous
  • Crystal system: Triclinic crystal system
  • Chemical formula: KAlSi₃O₈
  • Hardness (Mohs hardness scale): 6 – 6.5

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 results from small quantities of lead and water in the feldspar.

Properties

  • Chemical Formula: KAlSi3O8
  • Crystal System: Triclinic
  • Refractive Index: 1.52 – 1.53
  • Transparency: Translucent to opaque
  • Double Refraction: -.008
  • Luster: Vitreous
  • Cleavage: 2,1 – basal ; 2,1 – prismatic
  • Mineral Class: Microcline

Occurrence

Amazonite is a mineral of limited occurrence. Formerly it was obtained almost exclusively from the area of Miass in the Ilmensky Mountains, 50 miles southwest of Chelyabinsk, Russia, where it occurs in granitic rocks. More recently, high-quality crystals have been obtained from Pike’s Peak, Colorado, where it is found associated with smoky quartz, orthoclase, and albite in a coarse granite or pegmatite. Crystals of amazonite can also be found in Crystal Park, El Paso County, Colorado. Other locations in the United States which yield amazonite include the Morefield Mine in Amelia, Virginia. It is also found in pegmatite in Madagascar, Canada and in Brazil.

Because of its bright green color when polished, amazonite is sometimes cut and used as a cheap gemstone, although it is easily fractured, and loses its gloss due to its softness.

 

Information Source: