Latitude & Longitude:
11° North , 38° East (est.)
Estimate based on other nearby localities or region boundaries.
Margin of Error:
Opal nodules mined from rhyolitic rock.
Formerly in Showa region.
Opals from here, called chocolate opal because of the chocolate colour inside the nodules, came on the market in the early 1990s.
Select Mineral List TypeStandard Detailed Strunz Dana Chemical Elements
Detailed Mineral List:
Formula: SiO2 · nH2O
Reference: Gem Information, 23 May 2007 (Japan Germany Gemmological Laboratory), 20-24.
List of minerals arranged by Strunz 10th Edition classification
|Group 4 - Oxides and Hydroxides|
|ⓘ||Opal||4.DA.10||SiO2 · nH2O|
List of minerals arranged by Dana 8th Edition classification
|Group 75 - TECTOSILICATES Si Tetrahedral Frameworks|
|Si Tetrahedral Frameworks - SiO2 with H2O and organics|
|ⓘ||Opal||188.8.131.52||SiO2 · nH2O|
List of minerals for each chemical element
|H||ⓘ Opal||SiO2 · nH2O|
|O||ⓘ Opal||SiO2 · nH2O|
|Si||ⓘ Opal||SiO2 · nH2O|
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