Obsidian
Volcanic Glass (70% or more SiO2)
igneous
Category
Minerals
Browse minerals specimens identified by the Rock Identifier community.
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Magnetite
Magnetite (Fe3O4)
mineral
Slate
Slate (foliated metamorphic rock)
metamorphic
Labradorite (in Larvikite or Gabbro)
Plagioclase Feldspar (containing (Ca, Na)(Al, Si)4O8)
igneous
Chert (with Quartz Veining)
Microcrystalline Quartz (SiO2)
sedimentary
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Olivine (Peridotite)
(Mg,Fe)2SiO4 (Magnesium Iron Silicate)
igneous
Obsidian
Volcanic glass (mainly SiO2 with inclusions)
igneous
Chert (Flint)
Silicon dioxide (SiO2)
sedimentary
Slate
Slate (foliated metamorphic rock)
metamorphic
Olivine (Peridotite)
(Mg, Fe)2SiO4 (Magnesium Iron Silicate)
igneous
Milky Quartz
Quartz (Silicon Dioxide, SiO2)
mineral
Magnetite
Iron(II,III) oxide (Fe3O4)
mineral
Quartz (Citrine variety)
Silicon Dioxide (SiO2)
mineral
Snowflake Obsidian
Spherulitic Volcanic Glass (primarily SiO2 with Cristobalite inclusions)
igneous
Petrified Wood
Silicified Wood (primarily SiO2 - Silicon Dioxide)
sedimentary
Chert nodules in Limestone
Microcrystalline Quartz (SiO2) in Calcium Carbonate (CaCO3) matrix
sedimentary
Clear Quartz
Silicon Dioxide (SiO2)
mineral
Pyrite with Iron Oxides (Fool's Gold in Matrix)
Iron Sulfide (FeS2)
mineral
Snowflake Obsidian
Volcanic Glass with Cristobalite inclusions (70–75% SiO2)
Igneous
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Red Sandstone
Arenite (Ferruginous Sandstone)
sedimentary
Sandstone (Quartz-rich)
Arenite (composed primarily of SiO2)
sedimentary
Chert (Iron-stained)
Microcrystalline quartz (SiO2)
sedimentary
Garnet in Schist
Almandine Garnet in Mica-Schist (Fe3Al2(SiO4)3)
metamorphic
Petrified Wood
Silicified Wood (SiO2)
sedimentary
Greenstone
Metabasalt / Greenschist facies rock
metamorphic
Milky Quartz Pebble
Silicon Dioxide (SiO2)
mineral
Petrified Wood
Silicified Wood (primarily SiO2)
sedimentary
Magnetite
Magnetite (Fe3O4)
mineral
Note: Image shows a biological specimen (Rat), not a rock. Representative geological equivalent: Galena (due to lead-grey colors in fur).
Galena (PbS)
mineral
Olivine (Peridotite/Dunite)
Olivine (Mg,Fe)2SiO4 within Peridotite
igneous
Petrified Wood
Silicified wood (principally SiO2)
sedimentary
Magnetite / Ironstone
Magnetite (Fe3O4)
mineral
Chert (Flint)
Microcrystalline Quartz (SiO2)
sedimentary
Lepidolite in Quartz (Lithium-bearing Ore)
Lepidolite (K(Li,Al)3(Al,Si,Rb)4O10(F,OH)2) and Quartz (SiO2)
igneous/mineral
Chert (White Chert)
Silicon Dioxide (SiO2)
sedimentary
Chert (Jasper/Mudstone variety with Oxidation)
Silicon dioxide (SiO2)
sedimentary
Pearl
Nacre (Aragonite and Conchiolin), CaCO3
mineral
Agate (Moss or Dendritic Agate)
Chalcedony (Silicon Dioxide, SiO2)
mineral
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Unakite
Unakite (Epidotized Granite)
metamorphic