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Gemstones 250x250

The Mineral chrysocolla

Chrysocolla Quartz on Matrix

Chrysocolla is a sharply colored mineral. Its color can be among the brightest shade of blue and green, and is caused by its copper content. Chrysocolla is often coated by a drusy layer of glossy clear Quartz, or intergrown together with the Quartz.

The chemical formula for Chrysocolla is not clearly defined, as it contains a varying substitution of elements and water content in its chemical structure. Though a more definitive form of Chrysocolla with an identifiable chemical formula can exist in microcrystals, most forms are considered amorphous. Multiple analyses of different compositions have been offered over the years.

For additional information, see the gemstone section on Chrysocolla.

Chemical Formula

Cu2H2Si2O5(OH)4

Color

Bright green, bluish-green, sky blue, gray. May be mottled or multicolored green and blue.

Crystal System

Orthorhombic

Properties

Streak
White to pale blue
Hardness
2 - 4
Transparency
Translucent to Opaque
Specific Gravity
2.0 - 2.2
Luster
Vitreous to greasy
Cleavage
None
Fracture
Conchoidal to uneven
Tenacity
Brittle

Crystal Habits

Chrysocolla is never in visible crystals. It is almost always in botryoidal, reniform, or stalactitic groups, in rounded balls, and in massive form. Also in solid and fibrous veins, in tufts of fibrous crystals, and in crusts. Frequently forms pseudomorph after other minerals, especially Azurite.

Additional Information

Composition
Basic copper silicate, often with some aluminum. The composition of this mineral is usually variable and it therefore lacks a definitive chemical composition.
In Group
Silicates; Phyllosilicates
Striking Features
Bright color, hardness, and habits
Environment
As a secondary alteration mineral in the oxidation zone of copper deposits, hydrothermal replacement deposits, and in igneous rocks.
Rock Type
Igneous, Sedimentary, Metamorphic

Varieties

 -   Greenish-blue mixture of Chrysocolla, Turquoise and other copper minerals such as Malachite from the copper mines near Eilat in Israel.

Uses

Chrysocolla is used as a minor gemstone and may be fashioned into beads and cabochons. It is also occasionally faceted into other gemstone forms for collectors. Although Chrysocolla's colors is very unique and attractive, its low hardness limits its use as a gemstone. The gemstone forms are associated with harder Quartz and are also more stable.

Chrysocolla occurs in many important copper deposits, and is an ore of copper.

Noteworthy Localities

Most Chrysocolla is from copper deposits in arid regions, though it is not at all limited to these regions and is found worldwide. Outstanding Chrysocolla in reniform blobs and thick crusts comes from Kolwezi, Katanga (Shaba), Congo (Zaïre). The ancient Timna Copper Mines of Eilat, Israel, have produced Chrysocolla combined with other copper minerals in a combination that has been given the trade name Eilat Stone. Excellent Chrysocolla pseudomorphs after Azurite come from the Whim Creek Copper Mine, Whim Creek, Western Australia. Important South American localities include the Lily Mine, Pisco Umay, Peru; and several deposits within Chañaral Province, Atacama Region, Chile.

The most outstanding Chrysocolla has come from many of the classic Arizona copper mines. The most noteworthy and outstanding are the Inspiration Mine, Globe-Miami District, Gila Co.; the 79 Mine, Hayden, Gila Co.; Morenci, Greenlee Co.; and Ray, Pinal Co. The locality of Ray is especially noted for its beautiful and intriguing stalagmites combined with Quartz.

Common Mineral Associations

Quartz, Malachite, Azurite, Limonite, Turquoise

Distingushing Similar Minerals

Variscite - Usually greener in color.
Turquoise - Harder.
Blue and green Chalcedony - Much harder.
Allophane - Can be very difficult to distinguish.
Smithsonite - Slightly harder and usually lighter in color; otherwise may be difficult to distinguish.


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