ClassicGems.net

Ajoite

Discovered in 1958;   IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

(K;Na)Cu₇AlSi₉O₂₄(OH)₆ · 3(H₂O)

Hydrated Potasium Sodium Copper Aluminum Silicate Hydroxide

Molecular Weight:

3,926.74 gm

Composition:

Potassium

2.24 %

K

2.70 %

K₂O

Sodium

1.02 %

Na

1.38 %

Na₂O

Aluminum

2.06 %

Al

3.89 %

Al₂O₃

Copper

32.37 %

Cu

40.51 %

CuO

Silicon

20.74 %

Si

44.37 %

SiO₂

Hydrogen

0.82 %

H

7.34 %

H₂O

Oxygen

40.74 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/D.07-10

Nickel-Strunz 10th Ed. ID:

9.EA.70

9 : SILICATES (Germanates)
E : Phyllosilicates
A : Single nets of tetrahedra with 4-, 5-, (6-), and 8-membered rings

Related to:

n/a

Varieties:

None

Synonyms:

None

Crystal Data

Crystallography:

Triclinic - Pinacoidal

Crystal Habit:

As sprays of bladed prismatic crystals, to 0.4 mm; commonly fibrous; Lath - Shaped like a small, thin plaster lath, tabular (rectangular) in shape; Massive - Uniformly indistinguishable crystals forming large masses; Platy - Sheet forms (e.g. micas)

Twinning:

None

Physical Properties

Cleavage:

Perfect on [010]

Fracture:

n/a

Tenacity:

Brittle

Moh's Hardness:

3.5

Density:

2.96 (g/cm³)

Luminescence:

None

Radioactivity:

Barely Detectable; GRapi = 31.60 (Gamma Ray American Petroleum Institute Units)

Optical Properties

Color:

Bluish Green, Light Green

Transparency:

Translucent

Luster:

Vitreous (Glassy)

Refractive Index:

1.550 - 1.641  Biaxial ( + )

Birefringence:

0.0910

Dispersion:

Strong, r < v

Pleochroism:

Visible; X = very light bluish green; Y = Z = brilliant bluish green

Occurances

Geological Setting:

In oxidized copper-rich base-metal deposits.

Common Associations:

Shattuckite, Conichalcite, Quartz, Muscovite, Pyrite (Ajo, Arizona, USA); creaseyite, Fluorite (Potter-Cramer property, Arizona, USA); Shattuckite, Duhamelite, Sillénite (Munihuaza, Mexico); Quartz, Papagoite (Messina, South Africa).

Common Impurities:

Fe, Mn, Ca

Type Locality:

New Cornelia Mine (Ajo Mine), Ajo, Little Ajo Mts, Pima Co., Arizona, USA

Year Discovered:

1958

View mineral photos:

Ajoite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Ajoite is a rare and beautiful mineral that is usually found in association with other rare secondary copper minerals such as Papagoite and Shattuckite. A single specimen containing these minerals together is an amazing and beautiful combination of colors. Ajoite forms as excellent microcrystal specimens and occassionally as relatively large masses or veins in Quartz that can be fassioned into beautiful cabochons.

Ajoite is only found in a few locations worldwide. Of course it is found at the type locality New Cornelia Mine, Ajo, Pima County, Arizona and also at Wickenburg, Maricopa County, Arizona, USA; Munihuaza, near Alamos, Sonora, Mexico; and Messina, Transvaal, South Africa.

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