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| 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." |
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Classification
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Mineral
Classification: |
Oxides
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Strunz 8th
Ed. ID:
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4/D.01-80 |
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4 : Oxides & Hydroxides D : Oxides with metal : oxygen =
1:2 (MO2 and related compounds) 01 : Quartz group
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Crystal
Data
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Crystallography:
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Amorphous
(no crystalline forms) |
Crystal
Habit:
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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.
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Physical
Properties
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Cleavage: |
None
(amorphous)
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Fracture: |
Conchoidal
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Tenacity:
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Brittle
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Moh's
Hardness: |
5.5
- 6.0
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Density:
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1.90 - 2.30 (g/cm3) |
Radioactivity:
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Not
Radioactive
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Optical
Properties
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Color: |
Colorless,
white, yellow, orange, red, yellowish brown, greenish,
blue, gray, black, violet. |
Transparency: |
Transparent
to Translucent to Opaque
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Luster: |
Vitreous,
Waxy, Pearly, Dull |
Refractive
Index: |
1.43
Isotropic |
Birefringence: |
0.00
(Isotropic)
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Dispersion: |
Weak
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Pleochroism: |
Distinct;
red, orange, yellow, green, blue
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Occurances
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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 |
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More
Information
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Mindat.org Webmineral.com |
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This
page contains Opal gems from Brazil and Mexico.
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We
have not photographed our Brazil and Mexican Opal
gems yet. Please check back soon!
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