THE MINERAL CHRYSOCOLLA

Chemistry: CuSiO3 - nH2 O, Hydrated copper silicate
Class: Silicates
Subclass: Phyllosilicates
Uses: minor ore of copper and an ornamental stone.
Specimens

Chrysocolla is attractive blue-green that provides a unique color to the mineral world. Chyrsocolla is perhaps more appropriately a mineraloid than a true mineral. Most of the time it is amorphous meaning that it does not have a coherent crystalline structure. However at higher temperatures it does demonstrate a distorted crystal structure that seems to be composed of Si4 O10 sheets. Chrysocolla forms in the oxidation zones of copper rich ore bodies.

Pure chrysocolla is soft and fragile and therefore not appropriate for use in jewelry. However, chrysocolla often is "agatized" in chalcedony quartz and it is the quartz that provides the stone with its polish and durability. Druzy Chrysocolla is a rock composed of agatized chysocolla with a crust of small sparkling quartz crystals in small cavities. A skilled craftsman, if able to polish a specimen that accentuates the colored swirles of chrysocolla and sparkles of the druzy quartz, can produce a lovely and valuable piece of jewelry. Occasionally, chrysocolla can have a turquoise color and be used as a fraudulent substitute for the more precious stone.

PHYSICAL CHARACTERISTICS:

Color is a unique green-blue but can vary widely from more blue to more green, often in the same specimen.
Luster is earthy to dull or vitreous and waxy.
Transparency specimens are translucent to opaque.
Crystal System is probably monoclinic or orthorhombic.
Growth Habits include mostly massive forms that can be crusts, stalachtites and botryoidal. Also as inclusions in other minerals such as quartz.
Cleavage is absent.
Fracture is pronounced conchoidal.
Hardness is variable from 2 to 4.
Specific Gravity is approximately 2.0 - 2.3 (very light)
Streak is white to blue-green.
Associated Minerals are quartz, limonite, azurite, malachite, cuprite and other secondary copper minerals.
Other Characteristics: may have an opal like appearance.
Notable Occurrences include Arizona, Utah, New Mexico and Pennsylvania, USA; Isreal; Zaire and England.
Best Field Indicators are lack of crystals, color, fracture, low density and softness.

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