Garnet (likely Almandine, Pyrope, or a blend)
Garnet group minerals: X3Y2(SiO4)3, where X and Y represent various metal ions (e.g., Almandine: Fe3Al2(SiO4)3, Pyrope: Mg3Al2(SiO4)3)
Mineral
Category
Sedimentary (Secondary Formation)
Browse sedimentary (secondary formation) specimens identified by the Rock Identifier community.
Quartz (likely)
Quartz (SiO2 - Silicon Dioxide)
Mineral
Chalk
Calcareous Ooze (composed primarily of coccoliths)
Sedimentary Rock
Micaceous Sandstone or Quartzite
Sandstone (lithified quartz grains, often with mica) or Quartzite (metamorphosed sandstone)
Sedimentary or Metamorphic
River Rock (Quartz-dominated)
Silicon Dioxide (SiO2) mixture with varied clastic sediments
sedimentary (alluvial deposit)
Chert (or Flint)
Chert (a cryptocrystalline variety of quartz, SiO2)
sedimentary
Puddingstone
Conglomerate (specifically a type of jasper conglomerate or quartz conglomerate)
Sedimentary
Quartz
SiO₂ (Silicon Dioxide)
Mineral
Quartz (pebble)
Quartz (SiO₂)
Mineral
Quartz (Milky Quartz)
Quartz (SiO2 - Silicon Dioxide)
Mineral
Hematite (beads)
Hematite (Fe₂O₃)
Mineral
Chert (varietal known as Jasper or Flint)
Silicon Dioxide (SiO2)
Sedimentary Rock
Red Jasper
Jasper (a variety of Chalcedony, SiO₂ with impurities)
Mineral
Banded Agate (variety of Chalcedony)
Agate (SiO2)
mineral
Quartz
Quartz (SiO2)
Mineral
Banded Gneiss
Gneiss (pronounced "nice")
metamorphic
Fluorite
Calcium Fluoride (CaF2)
mineral
Pyrite
Iron Pyrite (FeS2)
Mineral
Chalcedony
Chalcedony (SiO₂)
Mineral
Green Slag Glass (Cullet)
Amorphous Silica (Industrial Glass Byproduct)
Synthetic/Byproduct (Non-igneous, non-sedimentary, non-metamorphic)
Aquamarine and clear quartz
Aquamarine (Be3Al2Si6O18), Quartz (SiO2)
Mineral
Anthracite Coal
Anthracite (a variety of coal, predominantly carbon)
Sedimentary Rock (Metamorphosed)
Chert (variant of Flint)
Chert (SiO2)
Sedimentary
Sandstone
Sandstone (arenite is a more specific geological term for a clean sandstone, while wacke refers to a dirty sandstone with significant matrix)
Sedimentary
Pyrite (Fool's Gold)
Iron Disulfide (FeS2)
mineral
Hematite Beads
Hematite (Fe2O3)
Mineral
Red Jasper (beads)
SiO₂ (Silicon Dioxide)
Mineral, variety of chalcedony (microcrystalline quartz)
Quartz
Silicon Dioxide (SiO2)
Mineral
Quartz Druzy Geode
Silicon Dioxide (SiO2) - Crystalline Variety
mineral
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
Coal (most likely Bituminous or Anthracite)
Bituminous Coal (Grade of Coal), Anthracite (Grade of Coal)
Sedimentary Rock
Cherry Creek Jasper (also known as Red Creek Jasper or Cherry Creek Agate)
Jasper, microcrystalline quartz (SiO₂)
Sedimentary Rock
Cobaltoan Calcite / Pink Dolomite (Possible)
Cobaltoan Calcite: (Ca,Co)CO3; Pink Dolomite (or Thulite): CaMg(CO3)2 or Mn-Dolomite / (Thulite: Mn2+3Al2(Si2O7)(SiO4)O(OH))
Mineral / Rock (depending on purity)
Jasper
Jasper (a variety of Chalcedony, SiO2)
Mineral
Geode (Unopened)
Silica Concretion / Geode (Formula: SiO2 for quartz internal contents)
sedimentary
Clay (as a rock-forming material)
Clay minerals (e.g., Kaolinite group, Smectite group, Illite group, Chlorite group)
Mineral
Quartz (likely Milky Quartz)
Quartz (SiO₂ - Silicon Dioxide)
Mineral
Pyrite
Iron Disulfide (FeS2)
mineral
Thunderegg (Agate-filled Geode Node)
Silicon dioxide (SiO2) with various inclusions
sedimentary/igneous association
Dark Igneous Rock (Likely Basalt or Diabase)
Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.
Igneous
Epidote (or Epidote-rich rock)
Epidote. Mineral formula: Ca2(Al,Fe)3(SiO4)3(OH).
Mineral, often found in metamorphic rocks but also in sedimentary and igneous rocks
Muscovite Mica
Muscovite (KAl2(AlSi3O10)(OH)2)
Mineral