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THE MINERAL AJOITE

  • Chemistry: (K, Na)Cu7Al(Si3O8) 3(OH)6 - 3H2O, Hydrated Potassium Sodium Copper Aluminum Silicate Hydroxide
  • Class: Silicates
  • Subclass: Phyllosilicates?
  • Uses: A very minor ore of copper and as mineral specimens.
  • Specimens

Ajoite is an attractive copper silicate mineral that is named for its type locality in the Ajo District of Pima County, Arizona. It is a secondary mineral that forms from the oxidation of other secondary copper minerals.

Ajoite forms excellent microcrystal specimens. The small prismatic crystals are often arranged in tufts with an almost aquamarine-like blue green color. It is associated with other rare and colorful minerals such as shattuckite, copper, papagoite and plancheite; which makes specimens even more attractive.

The color variety in a single multi-mineral specimen is sometimes surreal. Massive samples of ajoite are also unique and are sometimes carved or tumbled and can be used as an ornamental stone. Ajoite's classification as a phyllosilicate is questionable as its true structure is as yet unknown.

PHYSICAL CHARACTERISTICS:

  • Color is blue-green to light green.
  • Luster is dull to vitreous.
  • Transparency specimens are transparent to translucent.
  • Crystal System is triclinic, bar 1.
  • Growth Habits include acicular to thin prismatic crystals often found as spherules or sprays of acicular radial crystal clusters and as massive specimens.
  • Cleavage is perfect.
  • Hardness is 3.5.
  • Specific Gravity is approximately 2.9 - 3.0 (average for non-metallic minerals).
  • Streak is pale greenish white.
  • Associated Minerals are quartz, limonite, mimetite, phoenicochroite, willemite, wickenburgite, shattuckite, copper, papagoite, plancheite, duftite and other secondary copper minerals.
  • Notable Occurrences are limited to the New Cornelia Mine, Ajo District, Pima County and Wickenburg, Maricopa County, Arizona, USA and the Messina District, South Africa.
  • Best Field Indicators are color, crystal habit, locality and associations.

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