Blue chalcedony cabochon (probable)
Chalcedony, a cryptocrystalline variety of quartz; silicon dioxide, SiO₂
gemstone
Category
Sedimentary (With Some Aspects Of Mineral Replacement)
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Ironstone Concretion / Limonite-stained Siltstone
Ironstone (primarily Limonite FeO(OH)·nH2O and Siltstone)
sedimentary
Fossil bivalve shell
Ribbed pectinid or related bivalve; originally calcite/aragonite (CaCO₃), likely partially mineralized
fossil
Iron-rich chert or weathered ironstone
Chert (microcrystalline quartz, SiO₂) with iron-oxide minerals
sedimentary
Chert (often called Jasper or Flint)
Microcrystalline Silica (SiO2)
sedimentary
Chert Arrowhead
Cryptocrystalline Quartz (SiO2)
sedimentary
Chert (Flint)
Silicon Dioxide (SiO2)
sedimentary
Petrified Wood
Silicified Wood (SiO2)
sedimentary
Ammonite fossil
Fossilized ammonoid cephalopod; likely an involute ammonite, exact genus/species indeterminate
fossil
Fossil Rugose Coral (Horn Coral)
Order Rugosa (likely Grewingkia or Heliophyllum species); Calcium Carbonate (CaCO3)
sedimentary
Gneiss
Gneiss
metamorphic
Fossilized shell fragment
Likely a fossil mollusk shell; exact taxon cannot be determined from the image
fossil
Banded Gneiss
Metamorphic Gneiss
metamorphic
Likely bituminous coal
Coal, predominantly carbon-rich organic matter; exact rank cannot be confirmed visually
sedimentary
Sandstone
Arenite (SiO2 principal)
sedimentary
Petrified Wood
Silicified Wood (SiO2)
sedimentary
Banded Gneiss / Metamorphic River Pebble
Gneiss (Foliated Metamorphic Rock)
metamorphic
Vesicular basalt (possibly amygdaloidal basalt)
Basalt, a mafic volcanic rock composed mainly of plagioclase feldspar, pyroxene, and commonly olivine; cavities may contain secondary zeolites, calcite, or quartz.
igneous
Howlite
Howlite, Ca₂B₅SiO₉(OH)₅
mineral
Banded Gneiss
Gneiss (Metamorphic Rock)
metamorphic
Green Jasper
Silicon Dioxide (SiO2) with impurities
sedimentary
Chert / Flint
Microcrystalline Quartz (SiO2)
sedimentary
Milky quartz-bearing rock, likely quartzite or silicified limestone
Quartz (SiO₂), possibly in a quartzite or chalcedony-rich matrix
metamorphic
Chert (Flint)
Microcrystalline quartz (SiO2)
sedimentary
Polished brecciated jasper
Jasper, microcrystalline quartz (SiO₂), with iron-oxide and silica-rich breccia components
mineral
Unidentified weathered rock fragments
Likely mixed silicate rocks; specific identification requires testing
mineral
Gneiss
Gneiss
metamorphic
Sandstone (Ferruginous)
Arenite (with Iron Oxide)
sedimentary
Milky Quartz
SiO2 (Silicon Dioxide)
mineral
Chert (Jasper variety) with Iron Oxide staining
Cryptocrystalline Quartz (SiO2) with Goethite/Limonite impurities
sedimentary
Jasper
Silicon Dioxide (SiO2)
sedimentary
Orthoceratid Fossil in Limestone
Orthoceras (extinct genus of Nautiloid Cephalopod)
sedimentary
Ammonite Fossil
Ammonitida (Extinct subclass of Cephalopoda)
sedimentary
Likely iron-rich chert or jasper
Microcrystalline quartz (SiO₂), variably stained by iron oxides/hydroxides
sedimentary
Sandstone (Arkose)
Arkose Sandstone (SiO2 with KAlSi3O8)
sedimentary
Gneiss
Gneiss (High-grade Regional Metamorphic Rock)
metamorphic
Silty Shale
Silty Shale (Fissile Sedimentary Rock)
sedimentary
Yellow calcite
Calcite (calcium carbonate, CaCO₃)
mineral
Shale (with minor calcite veining)
Clastic sedimentary rock (primarily clay minerals and quartz)
sedimentary
Quartz-Veined Sandstone
Quartz-veined Arenite
sedimentary
Petrified Wood
Silicified Wood (SiO2)
fossil
Geode (Unopened)
Silica-rich concretion (SiO2)
sedimentary