Sedimentary Rock (Specifically A Concretion Or Possibly A Geode)

Basalt (tumbled/river-worn)

Mafic volcanic rock (primarily plagioclase feldspar and pyroxene)

Basalt (with Porphyritic/Vesicular texture)

Extrusive mafic igneous rock

Granite

Granitic intrusive igneous rock

Granite

Granite (Felsic Plutonic Rock)

Basalt

Basalt (Mafic Extrusive Igneous Rock)

Gastropod Steinkern (Internal Mold Fossil)

Gastropoda (Class); Internal mold or 'Steinkern' composed of Calcium Carbonate (CaCO3) or Sedimentary matrix

Basalt

Mafic Igneous Rock (composed primarily of Plagioclase and Pyroxene)

Pumice

Pumice (a highly vesicular felsic volcanic rock)

Quartz (Milky/Common)

Silicon Dioxide (SiO2)

Herkimer Diamond

Quartz (Silica - SiO2)

Basalt

Mafic Igneous Rock

Basalt

Mafic Igneous Rock

Basalt (River Stone)

Mafic volcanic rock

Basalt

Mafic Volcanic Rock

Pyrite in Shale

Iron Disulfide (FeS2)

Agate (specifically a Thunderegg/Agate Nodule)

Cryptocrystalline Quartz (SiO2)

Basalt

Basalt (Mafic volcanic rock)

Gneiss (specifically Amphibolite Gneiss)

Gneiss

Sandstone or Limestone

Arenite or Calcareous Sedimentary Rock

Basalt with Calcite Veining

Aphanitic Mafic Igneous Rock (Basalt) with CaCO3

Basalt River Pebble

Mafic Igneous Rock (Fine-grained Basalt)

Crushed Rock (Basalt)

Basalt (Aphanitic Mafic Igneous Rock)

Granite

Granite (felsic intrusive igneous rock)

Quartzite (Yellow/Orange variety)

Quartzite (primarily SiO2)

Basalt

Extrusive Mafic Igneous Rock

Serpentinite

Serpentinite (Mg, Fe, Ni, Al, Zn, Mn)2-3(Si, Al, Fe)2O5(OH)4

Basalt

Basalt (Aphanitic Mafic Igneous Rock)

Sandstone (Ferruginous)

Arenite with Iron Oxide (Limonite/Hematite) coating

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.

Shale (with Iron Oxide staining)

Fissile Mudstone (primarily Quartz and Clay minerals)

Pumice

Pumice (a highly vesicular extrusive igneous rock)

Basalt with Plagioclase Phenocrysts

Porphyritic Basalt

Basalt with Limonite stains

Extrusive mafic igneous rock; Limonite (FeO(OH)·nH2O)

Pumice

Pumice (Vesicular Rhyolite/Andesite)

Transit Token (RTD Denver)

Nickel-plated brass or bronze alloy (Cu-Sn-Zn-Ni)

Blue Lace Agate

Chalcedony (a form of Quartz) - SiO2

Basalt with Porphyritic Texture

Porphyritic Basalt

Pumice

Vesicular volcanic glass

Sandstone (lithic wacke)

Arenite / Lithic Wacke (mostly SiO2 with rock fragments)

Dalmatian Jasper / Dalmatian Stone

Peralkaline Rock (Silicon Dioxide with Amphibole inclusions)

Sandstone

Clastic Sedimentary Rock (composed mostly of SiO2)

Scoria (Red Lava Rock)

Scoria (Vesicular Basalt/Andesite)