Chalcedony (Common Opal or Agate variant)
Silicon Dioxide (SiO₂)
mineral
Category
Sedimentary (Secondary Formation)
Browse sedimentary (secondary formation) specimens identified by the Rock Identifier community.
Banded Gneiss
Gneiss (Metamorphic high-grade rock)
metamorphic
Yellow Jasper
Silicon Dioxide (SiO2) with Goethite/Iron oxide impurities
sedimentary (chemical)
Carnelian
Carnelian (SiO2 - Silicon Dioxide with Iron Oxide impurities)
mineral
Red Sandstone
Arenite (primarily Quartz and Feldspar with Iron Oxide cement)
sedimentary
Quartz (Milky or Cloudy Quartz)
Silicon Dioxide (SiO2)
mineral
Sandstone
Arenite (a specific type of sandstone with less than 15% matrix)
Sedimentary rock
Chert or Flint (polished/water-worn)
Chert (a microcrystalline or cryptocrystalline variety of quartz, SiO2). Flint is a specific variety of chert.
Sedimentary (most likely, as Chert is a sedimentary rock often found as nodules in limestone or as bedded deposits; however, it can also form by metasomatic replacement, which leans towards metamorphic processes under certain conditions)
Quartz
Quartz (SiO2 - Silicon Dioxide)
Mineral
Pyrite
Iron Disulfide (FeS2)
mineral
River Cobble (Salt and Pepper Gneiss)
Gneiss (High-grade regional metamorphic rock)
metamorphic
Wood Jasper
Siliceous sedimentary rock (variety of Chert/Chalcedony)
Sedimentary
Labradorite (a variety of Feldspar)
Labradorite; (Na,Ca)(Al,Si)4O8 (a plagioclase feldspar)
igneous
Banded Chert (Ironstone/Jasper)
Cryptocrystalline Quartz (SiO2) with Iron Oxides
sedimentary
Gneiss
Gneissic Metamorphic Rock (Mineral composition: Quartz, Feldspar, Amphibole/Biotite)
metamorphic
Jasper with Agate Inclusions
Silicon Dioxide (SiO2) - variety of Quartz/Chert
sedimentary
Bog Iron / Limonite Concretion
Goethite/Limonite mixture (FeO(OH)·nH2O)
sedimentary
Banded Chert
Microcrystalline Quartz (SiO2)
sedimentary
Clear Quartz
Silicon Dioxide (SiO2)
mineral
Dalmatian Stone
Dalmatian Jasper (Aphanitic Igneous Rock with Arfvedsonite inclusions)
igneous
Quartz (likely a macrocrystalline variety like milky quartz or smoky quartz, given the appearance in the image)
Quartz (SiO₂ - Silicon Dioxide)
Mineral
Mica Schist
Mica Schist (KAl2(AlSi3O10)(OH)2 / K(Mg,Fe)3AlSi3O10(OH)2)
metamorphic
Sandstone Beach Pebble
Clastic Sandstone (SiO2 - Quartz-dominant)
sedimentary
Jasper
Jasper (Silicon Dioxide, SiO2)
sedimentary
Glauconitic Sandstone (or Greensand)
Glauconitic Siliciclastic Rock (Containing (K,Na)(Fe,Al,Mg)2(Si,Al)4O10(OH)2)
sedimentary
Milky Quartz
Quartz (Silicon Dioxide, SiO2)
mineral
Calcite
Calcite (CaCO₃)
Mineral
Carnelian
Carnelian (a variety of Chalcedony, SiO2)
Mineral
Quartz (Rock Crystal) with minor impurities
Quartz (SiO2)
Mineral
Fluorite (often referred to casually as 'Fluorspar' in industrial contexts)
Fluorite (CaF2)
Mineral
Blue Quartz
Quartz (SiO2) with inclusions
Mineral
Pyrite
Iron Disulfide (FeS2)
mineral
Gneiss
Gneiss
metamorphic
Chert (specifically Tan/Yellow Chert)
Chert (Microcrystalline or Cryptocrystalline Silica, SiO2)
sedimentary
Red Jasper (Banded Jasper)
Silicon Dioxide (SiO2) with Hematite impurities
sedimentary
Botryoidal Chalcedony (Agate/Desert Rose Chalcedony)
Silicon Dioxide (SiO2) - Cryptocrystalline Quartz
mineral
Botryoidal Chalcedony (Agate/Chert Nodule)
Chalcedony (SiO2)
mineral
Banded Gneiss
Gneiss (quartz-feldspar-biotite metamorphic rock)
metamorphic
Chert (or Flint)
Chert (cryptocrystalline quartz), SiO2
Sedimentary
Red Jasper
Silicon Dioxide (SiO2) with iron oxide inclusions
sedimentary
Dendritic Agate (or Dendritic Opal)
SiO2 (for Agate), SiO2·nH2O (for Opal)
Mineral
Red Jasper
Jasper (a variety of Chalcedony, SiO₂)
Mineraloid (cryptocrystalline quartz)