Organic (Geological Relative)

Browse organic (geological relative) specimens identified by the Rock Identifier community.

Crushed Limestone

Calcium Carbonate (CaCO3)

Sedimentary

Slate

Slate (a fine-grained, foliated metamorphic rock). Mineral composition: Primarily composed of mica minerals (muscovite, chlorite, sericite) and quartz, with minor amounts of hematite, pyrite, and other accessory minerals.

sedimentary

Chrysoprase

Chalcedony (cryptocrystalline quartz) with nickel inclusions; SiO2

Mineral

Chalcedony

Chalcedony (SiO₂)

Mineral

Amazonite

KAlSi3O8 (Potassium Feldspar, variety of Microcline)

Mineral

Sandstone

Sandstone (various mineral compositions)

Sedimentary

Cockle Shell (Fossil or Recent)

Class Bivalvia, Family Cardiidae (e.g., Cerastoderma edule for common cockle)

Sedimentary (Biogenic, a type of fossil)

Citrine

Quartz (SiO₂)

mineral

Red Chalcedony (likely dyed)

Chalcedony (a variety of Quartz), SiO2

Mineral (Cryptocrystalline Quartz)

Blue Chalcedony

Chalcedony (a cryptocrystalline variety of Quartz - SiO₂)

Mineral

Serpentinite (Serpentine Rock)

Serpentinite is a rock composed of one or more serpentine group minerals, chiefly antigorite, chrysotile, and lizardite, with the general formula (Mg,Fe)3Si2O5(OH)4. Often includes other minerals like magnetite, talc, and chromite.

Metamorphic Rock

Lepidolite

K(Li,Al)3(Si,Al)4O10(F,OH)2

Mineral

Coal

Coal (Sedimentary Rock / Organic Rock)

sedimentary

Calcite

Calcite (CaCO3)

Mineral

Pink Opal

Hydrated Silica (SiO2·nH2O)

mineral

Glauconitic Sandstone

Glauconitic Quartz Arenite (with K,Mg,Fe,Al silicate hydroxide)

sedimentary

Fluorite

Fluorite (CaF2)

mineral

Heart-shaped Limestone

Calcium Carbonate (CaCO3)

sedimentary

Azurite and Malachite

Azurite (Cu3(CO3)2(OH)2) and Malachite (Cu2CO3(OH)2)

mineral

Coal (Bituminous Coal)

Caustobiolith / Sedimentary Rock

sedimentary

Banded Limestone

Calcareous sedimentary rock (CaCO3)

sedimentary

Aragonite

Aragonite (Carbonate mineral), CaCO3

mineral

Sandstone with Liesegang Rings

Arenite with secondary Iron oxide (Limonite/Goethite) precipitation

sedimentary

Iron Ore / Ironstone Concretion

Mixture of iron oxide/hydroxide minerals, likely some combination of Hematite (Fe2O3), Goethite (α-FeOOH), and Limonite (a general term for hydrated iron oxides of variable composition) or potentially Bauxite (a mixture of aluminum hydroxides, often with iron oxides, (Al(OH)3) and FeO(OH)). The visual characteristics strongly suggest iron-rich material.

Mineral, specifically an iron ore

Ferruginous Sandstone (Ironstone)

Sedimentary rock with Limonite/Goethite cement

sedimentary

Shale

Mudstone (composed primarily of clay minerals like kaolinite, illite, and smectite, with quartz and calcite)

sedimentary

Polished amber-colored stone, possibly chert or jasper

Uncertain from image; likely microcrystalline quartz (SiO₂) if chert/jasper

mineral

Anthracite Coal

Anthracite

metamorphic

Fossiliferous Limestone

sedimentary

Banded gneiss, probably granitic gneiss

Foliated gneiss composed mainly of quartz (SiO₂), feldspar—orthoclase/microcline and plagioclase—and dark mica, commonly biotite K(Mg,Fe)₃AlSi₃O₁₀(F,OH)₂

metamorphic

Aventurine (likely Green Aventurine)

Quartz (SiO2) with included minerals (Fuchsite or Chlorite for green color)

Mineral

Quartz (possibly milky quartz)

Quartz (Silica; SiO₂)

Mineral

Schist

Schist (various mineral compositions)

metamorphic

Mixed Chalcedony and Jasper Bracelet (possibly 'Ocean Jasper' or similar banded variety for brown beads, and blue/grey Chalcedony for the translucent beads)

Chalcedony (SiO2), Jasper (SiO2 with impurities)

Mineral (specifically a cryptocrystalline variety of Quartz)