- 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.
Ajoite is an attractive copper silicate mineral that is named for its type locality in the Ajo District of Pima County,
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
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.
- 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,
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.