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 - Crocoite.com Mineral Locations 7 - Glendale Community College 8 -Google Images 9 -Google Scholar 10 -MinDAT 11 -MinMax(Deutsch) 12 -MinMax(English) 13 - Mineral and Gemstone Kingdom 14 -Mineralienatlas (Deutsch) 15 - Minerals of Wisconsin 16 - Philatelic Mineralogy 17 -QUT Mineral Atlas 18 - Scandinavian mineral gallery 19 - Tradeshop.com - The Rainbow of Gems 20 -University of Texas at Austin 21 -theimage Search for Opal using: Visit our Advertisers for Opal : Translate Opal Mineral Data : Ask about Opal here : Print or Cut-and-Paste your Opal Specimen Label here :
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