Opal
Hydrous silicon dioxide (SiO2·nH2O)
mineral
Category
Mineralized Fossil
Browse mineralized fossil specimens identified by the Rock Identifier community.
Learn about Mineralized Fossil in the encyclopedia
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Quartz
SiO₂ (Silicon Dioxide)
Mineral
Chert (White Chert/Flint)
Chert (Microcrystalline or Cryptocrystalline Quartz, SiO2)
sedimentary
Chalk / Sedimentary Limestone
Calcium Carbonate (CaCO3) - Biogenic Sedimentary Rock
sedimentary
Slate
Slate (Metamorphic Rock)
metamorphic
Limestone
Calcium Carbonate (CaCO3)
sedimentary
Petrified Wood
Silicified Wood (SiO2)
sedimentary
Chalk
Calcium Carbonate (CaCO3)
sedimentary
Chert (Iron-stained)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
sedimentary
Sandstone
Sandstone (lithified sand)
sedimentary
Sandstone
Arenite (a specific type of sandstone with less than 15% matrix)
Sedimentary rock
Quartz (chalcedony variety) or Limestone with Quartz Veins
SiO2 (for Quartz/Chalcedony); CaCO3 (for Limestone)
Mineral or Sedimentary Rock (with mineral inclusions)
Petoskey Stone
Hexagonaria percarinata (Fossilized Rugose Coral)
sedimentary
Petrified Wood
Silicified wood (Quartz/Chalcedony)
Sedimentary
Crushed Limestone
Calcium Carbonate (CaCO3)
Sedimentary
Petoskey Stone
Hexagonaria percarinata (Fossilized Coral)
sedimentary
Petrified Wood
Silicified Wood (SiO2 permineralization)
sedimentary
Limestone
Calcium Carbonate (CaCO3)
sedimentary
Sandstone (Pebble)
Sandstone (arenite, arkose, wacke depending on composition)
sedimentary
Amber
(C10H16O)n – an amorphous organic substance, primarily composed of polymerized isoprenoids.
Mineral
Limestone
Calcium Carbonate (CaCO3)
sedimentary
Chert (within Asphalt)
Chert (SiO2)
sedimentary
Sandstone
Sandstone (lithified arenite/wacke)
Sedimentary Rock
Chert (Flint)
Chert (microcrystalline quartz)
sedimentary
Sandstone
Sandstone (clastic sedimentary rock, composed predominantly of sand-sized minerals or rock fragments)
Sedimentary Rock
Limestone
Calcium Carbonate (CaCO3)
sedimentary
Sandstone
Sandstone (Clastic Sedimentary Rock)
Sedimentary Rock
Sandstone
Sandstone (arenite is a more specific geological term for a clean sandstone, while wacke refers to a dirty sandstone with significant matrix)
Sedimentary
Sandstone (Pebble/Cobble)
Sandstone (arenite is a more precise term for sandstone with less than 15% matrix; this specimen appears to be a lithic or quartz arenite)
Sedimentary
Amber (Black)
Amber (succinite, retinite, etc., specifically, heavily included/dark varieties)
Mineraloid
Sandstone
Arenite or Sandstone
Sedimentary Rock
Chert
Siliceous sedimentary rock (predominantly microcrystalline quartz, SiO2)
Sedimentary
Iron Slag
Vitreous glassy waste (Fe-Si-Al-Ca compounds)
Mineral byproduct (anthropogenic / techno-fossil)
Coal (most likely Bituminous or Anthracite)
Bituminous Coal (Grade of Coal), Anthracite (Grade of Coal)
Sedimentary Rock
Schist
Schist
Metamorphic
Red Coral
Corallium rubrum (for precious red coral), although other species like Corallium japonicum and Paracorallium are also used.
Organic Gemstone (not a rock or mineral in the traditional sense, but bio-mineralized material)
Banded Gneiss (River Rock/Pebble)
Gneiss (specifically a banded variety often found as a river rock)
Metamorphic Rock
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Nephrite Jade
Nephrite
Mineral/Rock
Potassium Feldspar (Orthoclase)
Orthoclase (KAlSi3O8)
mineral
Orthoclase Feldspar
Orthoclase (KAlSi3O8)
mineral