Common Opal
Hydrated amorphous silica (SiO2·nH2O)
Category
Browse metamorphic and igneous rocks specimens identified by the Rock Identifier community.
Common Opal
Hydrated amorphous silica (SiO2·nH2O)
Quartz
SiO2 (Silicon Dioxide)
Biotite on Matrix
Biotite (K(Mg,Fe)3AlSi3O10(F,OH)2)
Blue Apatite
Fluorapatite (Ca5(PO4)3F)
Pyrite
Iron Sulfide (FeS2)
Pyrite
Iron Sulfide (FeS2)
Potassium Feldspar
K-Feldspar (Orthoclase/Microcline) KAlSi3O8
Pyrite
Iron Sulfide (FeS2)
Mica (Muscovite)
Muscovite (KAl2(AlSi3O10)(OH)2)
Almandine Garnet
Almandine (Fe3Al2Si3O12)
Yellow Sapphire (Corundum)
Corundum (Aluminum Oxide, Al2O3)
Schist
Schist (Foliated Metamorphic Rock)
Garnet Rhyolite
Rhyolite (high-silica volcanic rock) with almandine/spessartine garnet
Almandine Garnet
Almandine, Fe3Al2(SiO4)3
Potassium Feldspar (Orthoclase)
Orthoclase (KAlSi3O8)
Muscovite Mica
Muscovite (KAl2(AlSi3O10)(OH)2)
Muscovite Mica (Golden/Yellow variety)
KAl2(AlSi3O10)(F,OH)2
Hematite
Iron(III) oxide (Fe2O3)
Garnet
Almandine/Pyrope Garnet (Silicate Mineral Group)
Epidotite (Unakite-related)
Epidote-rich rock
Epidote
{Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)
Garnet
Almandine (Fe3Al2(SiO4)3)
Ruby
Corundum (Al2O3 with Chromium traces)
Tumbled blue stone, possibly sodalite or blue quartz
Indeterminate from the photograph; possibilities include sodalite (Na₈Al₆Si₆O₂₄Cl₂) or blue quartz (SiO₂)
Magnetite / Iron Ore
Magnetite (Fe3O4)
Quartz
Quartz (SiO₂ - Silicon Dioxide)
Blue Sapphire
Corundum (Al2O3) with iron and titanium impurities
Specular Hematite (Specularite)
Iron(III) oxide (Fe2O3)
Garnet (likely Almandine or Pyrope)
Garnet (Group Name), Fe3Al2(SiO4)3 or Mg3Al2(SiO4)3
Pyrite
Iron Sulfide (FeS2)
Quartz
Silicon Dioxide (SiO2)
Quartz
Silicon Dioxide (SiO2)
Quartz-rich rock or quartz specimen
Quartz (SiO₂), likely massive quartz or quartz-bearing host rock
Gneiss
Gneissic Metamorphic Rock
Diopside (likely Chromian Diopside)
Diopside, part of Clinopyroxene family of inosilicates. Chemical formula: CaMgSi2O6. The green variety is often Chromian Diopside due to chromium impurities.
Tourmaline (likely Schorl)
Tourmaline Group Mineral (e.g., Schorl for black varieties); (Na,Ca)(Li,Mg,Fe,Mn,Al)3Al6(BO3)3Si6O18(OH)4
Garnet (Almandine)
Almandine (Fe3Al2(SiO4)3)
Garnet (Almandine)
Almandine (Fe3Al2(SiO4)3)
Magnetite (Iron Ore)
Magnetite (Fe3O4)
Red corundum (ruby-colored polished crystal)
Corundum, aluminum oxide (Al₂O₃); red color is typically caused by chromium
Ruby
Corundum (Al2O3 with Chromium traces)
Mica Schist
Mica Schist