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Opal: Africa, Australia, Ethiopia, Serbia, Tanzania, Turkey and other locations
Current inventory:  3 gems
 

Chemistry:  SiO₂ + 5-10% nH₂O

Prehistoric Discovery;   IMA status: Valid (pre-IMA; Grandfathered).
Opalus was the ancient Latin name probably derived from the Sanskrit word upala, meaning precious stone. The Greek word opallios literally means "to see a change of color."

Classification

Mineral Classification:

Oxides

Strunz 8th Ed. ID:

4/D.01-80

4 : Oxides & Hydroxides
D : Oxides with metal : oxygen = 1:2 (MO2 and related compounds)
01 : Quartz group

Crystal Data

Crystallography:

Amorphous  (no crystalline forms)

Crystal Habit:

Amorphous - (no crystalline forms) Habits include Massive; Concretions; Botryoidal; Stalactitic; Reniform - "kidney like" in shape (e.g. Hematite); cavity fillings (e.g. in fractures and geodes); replacement of other minerals or wood.

Physical Properties

Cleavage:

None (amorphous)

Fracture:

Conchoidal

Tenacity:

Brittle

Moh's Hardness:

5.5 - 6.0

Density:

1.90 - 2.30 (g/cm³)

Radioactivity:

Not Radioactive

Optical Properties

Color:

Colorless, white, yellow, orange, red, yellowish brown, greenish, blue, gray, black, violet.

Transparency:

Transparent to Translucent to Opaque

Luster:

Vitreous, Waxy, Pearly, Dull

Refractive Index:

1.43 Isotropic

Birefringence:

0.00 (Isotropic)

Dispersion:

Weak

Pleochroism:

Distinct; red, orange, yellow, green, blue

Occurances

Geological Setting:

Sedimentary and secondary from the alteration of high silica igneous extrusive rocks.

Type Locality:

n/a

Year Discovered:

Prehistoric discovery

View mineral photos:

Opal Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

This page contains Opal gems from Africa, Australia, Ethiopia, Madagascar, Serbia, Tanzania, Turkey and other locations. For more general information on Opals and Opals from other locations around the world, please visit our main Opal page.
 

  
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