Chert (Common Opal/Jasper transition)
Silicon Dioxide (SiO2)
Category
Browse sedimentary (with some aspects of mineral replacement) specimens identified by the Rock Identifier community.
Chert (Common Opal/Jasper transition)
Silicon Dioxide (SiO2)
Ammonite Fossil in Matrix
Ammonoidea subclass (e.g., Arietites or similar genera)
Chert (variously Flints)
Microcrystalline Quartz (SiO2)
Banded Gneiss
Gneiss (Metamorphic high-grade rock)
Sandstone (Ferruginous)
Arenite (SiO2 with Fe-oxide cement)
Concretion
Calcareous or ferruginous concretion
Sandstone (likely Graywacke or Arkose variant)
Clastic Sedimentary Rock (SiO2 with assorted lithic fragments)
Polished dark pebble, possibly basalt or chert
Uncertain; likely fine-grained basalt (plagioclase–pyroxene) or microcrystalline silica (chert)
Jasper
Silicon Dioxide (SiO2)
Gneiss
Gneiss
Sandstone Concretion
Clastic sedimentary rock (primarily Silica, SiO2, or Calcium Carbonate, CaCO3)
Flint or chert fragment
Microcrystalline quartz (SiO₂), commonly called flint when dark and nodular
Chert Pebble (Jasper or Agate variety)
Microcrystalline Quartz (SiO2)
Chert / Flint
Silicon Dioxide (SiO2)
Flint / Chert
Silicon dioxide (SiO2) - Microcrystalline Quartz
Chert (Common Opal/Chalcedony nodule)
Microcrystalline Quartz (SiO2)
Jasper
Microcrystalline Quartz (SiO2)
Flint
Microcrystalline quartz (SiO2)
Flint
SiO2 (Microcrystalline Quartz)
Flint
Silicon dioxide (SiO2) - Microcrystalline Quartz
Chert Arrowhead
Microcrystalline Quartz (SiO2)
Jasper
Microcrystalline Quartz (SiO2)
Chert Nodule
Microcrystalline Quartz (SiO2)
Chert (Flint)
Cryptocrystalline Quartz (SiO2)
Chert Pebble
Microcrystalline Quartz (SiO2)
Chalcedony (Chert/Flint variety)
Silicon Dioxide (SiO2)
Flint (within Limestone matrix)
Silicon dioxide (SiO2)
Yellow Chert (Jasper)
Chalcedony (SiO2) with iron oxide inclusions
Chert / Jasper
Microcrystalline Quartz (SiO2)
Red Jasper
Silicon Dioxide (SiO2)
Chert (Jasper variety)
Silicon Dioxide (SiO2)
Sandstone Beach Pebble
Clastic sedimentary rock (SiO2 with iron oxide cement)
Fossilized Coral (Favosites)
Favosites goldfussi / Tabulata
Polished operculum (“Shiva eye” shell)
Calcium-carbonate shell operculum, commonly from a turban snail (family Turbinidae); not a mineral specimen
Fossilized bivalve shell
Recrystallized calcium-carbonate shell, commonly fossil oyster or clam (Bivalvia)
Chert (with Iron Staining)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Polished orbicular jasper
Siliceous microcrystalline quartz (chalcedony), SiO₂, with iron-oxide and other mineral inclusions
Magnetite Orthorthotropic Rock
Magnetite (Fe3O4)
Jasper
Jasper / Silicon Dioxide (SiO₂)
Orange Calcite
Calcium Carbonate (CaCO3)
Chert (specifically Flint or Jasperoid)
Silicon Dioxide (SiO2)
Botryoidal Chalcedony
Silicon Dioxide (SiO2)