Material Index
| Name | Formula | Classifications | Members | Image | Lines | Spectra | Techniques | Tags |
|---|---|---|---|---|---|---|---|---|
| Opal | SiO2·nH2O | — | — | 18 | 1 | CL | Mineral, Hydrated | |
| Orthoclase | KAlSi3O8 | K feldspar | — | 17 | 1 | CL | Mineral, Aluminosilicate | |
| Orthopyroxene | (Mg,Mn,Fe)SiO3 | Pyroxene | Donpeacorite, Enstatite, Fe, Ferrosilite, Enstatite, Protoenstatite | 0 | 0 | — | Silicate, Subgroup | |
| Osmium | Os | — | — | 16 | 1 | SXES | Metal , Mineral , Element | |
| Osumilite | KFe2Al3(Al2Si10)O30 | Osumilite (group) | — | 0 | 0 | — | Mineral, Aluminosilicate | |
| Osumilite (group) | — | — | Friedrichbeckeite, Aluminosugilite, Oftedalite, Almarudite, Dusmatovite, Sugilite, Merrihueite, Poudretteite, Agakhanovite-(Y), Sogdianite, Eifelite, Armenite, Milarite, Shibkovite, Trattnerite, Brannockite, Yagiite, Roedderite, Klöchite, Osumilite-(Mg), Osumilite, Berezanskite, Chayesite, Darapiosite, Laurentthomasite | 0 | 0 | — | Group | |
| Osumilite-(Mg) | KMg2Al3(Al2Si10)O30 | Osumilite (group) | — | 0 | 0 | — | Mineral, Aluminosilicate | |
| Otavite | CdCO3 | Calcite (group) | — | 1 | 0 | — | Mineral, Carbonate | |
| Oxy-chromium-dravite | NaCr3(Cr4Mg2)(Si6O18)(BO3)3(OH)3O | Tourmaline | — | 0 | 0 | — | Mineral, Hydroxide , Borate | |
| Oxy-dravite | Na(Al2Mg)(Al5Mg)(Si6O18)(BO3)3(OH)3O | Tourmaline | — | 0 | 0 | — | Mineral, Hydroxide , Borate , Aluminosilicate | |
| Oxy-foitite | ☐(FeIIAl2)Al6(Si6O18)(BO3)3(OH)3O | Tourmaline | — | 0 | 0 | — | Mineral, Hydroxide , Borate , Aluminosilicate | |
| Oxy-schorl | Na(FeII2Al)Al6(Si6O18)(BO3)3(OH)3O | Tourmaline | — | 0 | 0 | — | Mineral, Hydroxide , Borate , Aluminosilicate | |
| Oxy-vanadium-dravite | NaV3(V4Mg2)(Si6O18)(BO3)3(OH)3O | Tourmaline | — | 0 | 0 | — | Mineral, Hydroxide , Borate | |
| Oxybismutomicrolite | (Bi1.33☐0.67)Σ2Ta2O6O | Microlite (group) | — | 0 | 0 | — | Mineral | |
| Oxycalciomicrolite | Ca2Ta2O7 | Calcium tantalate, Microlite (group) | — | 0 | 0 | — | Mineral |


