Prehnite
Prehnite (Ca2Al2Si3O10(OH)2)
mineral
Category
Mineral, Often Found As Detrital Grains In Sedimentary Rocks
Browse mineral, often found as detrital grains in sedimentary rocks specimens identified by the Rock Identifier community.
Black Sapphire (Basaltic Blue Sapphire)
Corundum (Al2O3)
mineral
Quartz Druzy on Matrix (likely Agate or Jasper)
Silicon Dioxide (SiO2) with various mineral inclusions
mineral
Basalt
Basalt (extrusive igneous rock)
Igneous
Garnet (Red Garnet)
Garnet Group. The red varieties seen in jewelry are typically Almandine (Fe3Al2(SiO4)3), Pyrope (Mg3Al2(SiO4)3), or a mix of the two (pyrope-almandine series).
Mineral (specifically, a variety of the mineral species Pyrope-Almandine Garnet)
Red Sandstone
Arenite (primarily Quartz with Iron Oxide coating)
sedimentary
Basalt (River Rock/Cobble)
Basalt (no specific mineral formula as it's a rock)
Igneous
Green Opal
Hydrated Silica (SiO2·nH2O)
mineraloid
Red Jasper
Silicon Dioxide (SiO2) with Iron Oxide (Fe2O3) inclusions
sedimentary
Selenite (Gypsum)
Hydrous calcium sulfate (CaSO4·2H2O)
mineral
Pyrulite (Pyrite / Chalcopyrite)
Iron Sulfide (FeS2) or Copper Iron Sulfide (CuFeS2)
mineral
Quartz (likely macrocrystalline variety)
Quartz (SiO₂)
Mineral
Serpentine, likely a variety of Chrysoprase (green chalcedony) or a similar translucent green mineral.
Serpentine Group Minerals (e.g., Antigorite, Lizardite) or Chalcedony (SiO2) with nickel impurities for Chrysoprase green.
mineral
Granite
Granite (Felsic Plutonic Rock)
igneous
Pink Garnet (likely Almandine or Rhodolite)
Garnet Group (Fe3Al2(SiO4)3 to Mg3Al2(SiO4)3)
mineral
Red Jasper
Silicon Dioxide (SiO2) with Iron inclusions
sedimentary
Common Opal (Green Opal / Pistachio Opal)
Hydrated silica (SiO2·nH2O)
mineraloid
Banded Chert (or Banded Jasper)
Silicon Dioxide (SiO2) with Iron Oxide impurities (Hematite/Goethite)
sedimentary
Diorite (Salt and Pepper Rock)
Diorite
igneous
Quartz Vein in Host Rock (Gabbro or Basalt)
Silicon Dioxide (SiO2) with Mafic Silicates
metamorphic/igneous
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Almandine Garnet
Almandine - Fe3Al2(SiO4)3
mineral
Hypersthene
(Mg,Fe)SiO3 - Enstatite-Ferrosilite series
mineral
Gold Ore in Quartz/Schist
Auriferous Quartz and Sulfide-bearing Schist
Metamorphic/Igneous (Hydrothermal)
Amygdaloidal Basalt with Agate/Chalcedony Infills
Amygdaloidal Basalt (Composition: SiO2 and (Mg,Fe)2SiO4 in matrix; SiO2 in amygdule)
igneous
Turquoise in Matrix
Hydrous phosphate of copper and aluminium, CuAl6(PO4)4(OH)8·4H2O
mineral
Prehnite
Prehnite (Ca2Al(AlSi3O10)(OH)2)
mineral
Chert (Jasper/River Pebble)
Silicon Dioxide (SiO2)
sedimentary
Quartz Geode/Druzy Quartz
Quartz (SiO₂)
Mineral
Labradorite
(Ca,Na)(Al,Si)4O8
mineral
Basalt
Mafic Igneous Rock (composed primarily of plagioclase, pyroxene, and olivine)
igneous
Basalt with Quartz Veins
Amygdaloidal Basalt (matrix) with Crystalline SiO2 (veins)
igneous
Red Jasper
Silicon Dioxide (SiO2) with iron oxide inclusions
sedimentary
Basalt (tumbled/river-worn)
Mafic volcanic rock (primarily plagioclase feldspar and pyroxene)
igneous
Quartzite
Quartzite (primarily SiO2)
metamorphic
Quartz (Milky Quartz)
Silicon Dioxide (SiO2)
mineral
Yellow Jasper
Silicon Dioxide (SiO2) with iron impurities
mineral
Quartzite (Yellow/Tan)
Metamorphic Rock composed of Quartz (SiO₂)
metamorphic
Basalt with Epidote (Greenstone)
Amygdaloidal Basalt (Ca2(Al, Fe)3(SiO4)3(OH) inclusions)
igneous
Agate
Cryptocrystalline Quartz (SiO2)
mineral
Milky Quartz
Quartz (Silicon Dioxide, SiO2)
mineral
Water and Silt (Sedimentary Environment)
Suspended Sediment / H2O (dihydrogen monoxide)
sedimentary