Opal Mineral Data + 
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- 75.2.1.1 Opal SiO2·n(H2O) None
- IV/D.01-10 Quartz SiO2 P 3121,P 3221 3 2
- IV/D.01-20 Tridymite SiO2 F1 1
- IV/D.01-30 Cristobalite SiO2 P 41212 4 2 2
- IV/D.01-35 Moganite! SiO2 I2/a 2/m
- IV/D.01-40 Melanophlogite SiO2·n(C,H,O,S) P 41/nbc 4/m 2/m 2/m
- IV/D.01-40* Melanophlogite-beta! SiO2·n(C,H,O,S) P m3n 4/m 3 2/m
- IV/D.01-50 Coesite SiO2 C 2/c 2/m
- IV/D.01-60 Stishovite SiO2 P 4/mnm 4/m 2/m 2/m
- IV/D.01-70 Lechatelierite* SiO2 None
- IV/D.01-80 Opal SiO2·n(H2O) None
General Opal Information |
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 Chemical Formula: |
SiO2·n(H2O) | ||
| Composition: |
Molecular Weight = 87.11 gm | ||
| Silicon 32.24 % Si 68.98 % SiO2 | |||
| Hydrogen 3.47 % H 31.02 % H2O | |||
| Oxygen 64.29 % O | |||
| ______ ______ | |||
| 100.00 % 100.00 % = TOTAL OXIDE | |||
| Empirical Formula: |
SiO2·1.5(H2O) | ||
| Environment: |
Sedimentary and secondary from the alteration of high silica igneous extrusive rocks. | ||
| IMA Status: |
Valid Species (Pre-IMA) Prehistoric | ||
| Locality: |
World wide occurrences. Link to MinDat.org Location Data. | ||
| Name Origin: |
From the Old Indian upala - "precious stone." | ||
| Synonym: |
Fire Opal - red | ||
| Hyalite - glassy | |||
| Hydrophane - porous | |||
| Prase - green | |||
| Precious opal - opalescent | |||
Opal Image | |||
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Opal Crystallography |
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| Crystal System: |
Amorphous- No Crystals | ||
Physical Properties of Opal |
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| Cleavage: |
None | ||
| Color: |
White, Yellow, Red, Brown, Blue. | ||
| Density: |
1.9 - 2.3, Average = 2.09 | ||
| Diaphaniety: |
Transparent to translucent to opaque | ||
| Fracture: |
Conchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz). | ||
| Habit: |
Amorphous - No crystalline form or imitative shape. | ||
| Habit: |
Massive - Uniformly indistinguishable crystals forming large masses. | ||
| Habit: |
Reniform - "Kidney like" in shape (e.g.. hematite). | ||
| Hardness: |
5.5-6 - Knife Blade-Orthoclase | ||
| Luminescence: |
Fluorescent, Short UV=greenish yellow, Long UV=white. | ||
| Luster: |
Vitreous - Dull | ||
| Streak: |
white | ||
Optical Properties of Opal |
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| Gladstone-Dale: |
CI meas= 0.177 (Poor) - where the CI = (1-KPDmeas/KC) KPDmeas= 0.2048,KC= 0.2489 |
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| Optical Data: |
Isotropic, n=1.43. | ||
Calculated Properties of Opal |
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| Electron Density: |
relectron=2.17 gm/cc |
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| Fermion Index |
Fermion Index = 0.01537 Boson Index = 0.98463 |
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| Photoelectric: |
PEOpal = 1.32 barns/electron |
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| Radioactivity: |
GRapi = 0 (Gamma Ray American Petroleum Institute Units) Opal is Not Radioactive |
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Opal Classification |
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| Dana Class: |
75.2.1.1 (75)Tectosilicate Si Tetrahedral Frameworks | ||
| (75.2)SiO2 with H2O and organics | |||
| (75.2.1)Dana Group | |||
| Strunz Class: |
IV/D.01-80 IV - Oxides | ||
| IV/D - Oxides with metal : oxygen = 1:2 (MO2 and related compounds) | |||
| IV/D.01 - Quartz group | |||
Other Opal Information |
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| References: |
NAME( Duda&Rejl90) PHYS. PROP.(Dana) OPTIC PROP.(Enc. of Minerals,2nd ed.,1990) | ||
| See Also: |
Links to other databases for Opal : 1 - Alkali-Nuts(English) 2 - Am. Min. Crystal Structure Database 3 - Amethyst Galleries' Mineral Gallery 4 - Athena 5 - CalTech Mineral Spectroscopy 6 - Glendale Community College 7 - Google Images 8 - Google Scholar 9 - MinDAT 10 - MinMax(Deutsch) 11 - MinMax(English) 12 - Mineral and Gemstone Kingdom 13 - Mineralienatlas (Deutsch) 14 - Philatelic Mineralogy 15 - QUT Mineral Atlas 16 - Ruff.Info 17 - Scandinavian mineral gallery 18 - Tradeshop.com - The Rainbow of Gems 19 - University of Texas at Austin 20 - theimage Search for Opal using: Visit our Advertisers for Opal : AA Mineral SpecimensB & L Fine Minerals Dan Weinrich Fine Minerals Dan Weinrich Auctions Excalibur Minerals Exceptional Minerals Fabre Minerals Greenside Minerals Heliodor John Betts Fine Minerals Mason's Minerals Mineral News Mineral of the Month Club MineralsWeb Fine Minerals The GeoZone Wrights Rock Shop Translate Opal Mineral Data : Ask about Opal here : Print or Cut-and-Paste your Opal Specimen Label here :
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