Rock (Likely Sedimentary)

Sandstone (likely Siltstone or Mudstone variety)

Clastic Sedimentary Rock (primarily SiO2 with iron oxides)

Biotite Schist (likely)

Biotite Schist (rock), Biotite (mineral)

Iron-rich breccia (likely hematite–goethite breccia)

Hematite (Fe₂O₃) and goethite (FeO(OH)) in a silicified or iron-cemented breccia

Likely polished dark stone or glassy mineral bead

Indeterminate; possibly obsidian, hematite, or a dark agate

Jasper

Silicon Dioxide (SiO2)

Rounded sandstone pebble

Quartz-rich sandstone (commonly arkosic or feldspathic sandstone)

Granite Pebble

Granite (Phaneritic Igneous Rock)

Sandstone (likely Arkosic or Quartzose)

Sandstone (SiO2 dominated)

Granite River Pebble

Granite

River Cobble (likely Sandstone or Siltstone type)

Sandstone or Siltstone (common rock types that form river cobbles)

Jasper (likely Ocean Jasper or Variegated Jasper)

Silicon Dioxide (SiO2) with impurities

Quartz with Host Rock

Silicon Dioxide (SiO2)

Banded chert or flint pebble

Microcrystalline quartz (SiO₂), likely chert with a pale weathered/altered zone

Weathered sandstone or limestone fragment

Indeterminate clastic carbonate/siliciclastic rock; likely quartz-rich sandstone or porous limestone

Tumbled jasper pebble

Silica-rich microcrystalline quartz/chalcedony, commonly brecciated or iron-stained jasper (SiO₂)

Weathered iron-rich rock, likely limonite/goethite-bearing laterite

Limonite–goethite aggregate, commonly approximated as hydrated iron oxides (FeO(OH)·nH₂O)

Quartz (Milky/Smoky variety on matrix)

Silicon Dioxide (SiO2)

River Stone (likely Siltstone or fine-grained Quartzite)

Sedimentary clastic rock containing SiO2 and iron oxides

Banded Chert (Jasper)

Silicon Dioxide (SiO2)

Orbicular rhyolite (likely)

Rhyolite, a silica-rich volcanic rock; commonly quartz, alkali feldspar, plagioclase, and iron-rich alteration minerals

Pumice (likely)

Pumice (extrusive igneous rock)

Red jasper-like chalcedony pebble

Microcrystalline quartz (SiO₂), likely iron-stained chalcedony/jasper

Likely weathered gray stone or chert fragment

Uncertain; possibly microcrystalline quartz (SiO₂)-rich chert

Porphyritic Basalt (Drill Core)

Porphyritic Basalt with Plagioclase Phenocrysts

Porphyritic Basalt

Basalt (with plagioclase or k-feldspar phenocrysts)

Polymictic breccia, possibly volcanic breccia

Polymictic clastic breccia; likely a matrix-supported breccia containing lithic fragments, quartz, feldspar, and dark mafic minerals

Shale (or Mudstone/Siltstone)

Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)

Shale

Shale (clastic sedimentary rock)

Quartz with Mica inclusions (likely Schist or Gneiss host)

Silicon Dioxide (SiO2) with Phyllosilicates (KAl2(AlSi3O10)(OH)2)

Likely limestone or calcareous fossil fragment

Calcite-rich carbonate rock; possibly bioclastic limestone (CaCO₃)

Iron-stained quartz-rich rock, possibly jasper or chert

Microcrystalline quartz (SiO₂) with iron oxides/hydroxides

Tumbled jasper (likely brecciated or orbicular jasper)

Microcrystalline quartz (SiO₂), with iron-oxide inclusions

Likely weathered quartz-bearing rock fragment

Indeterminate; appears to contain quartz (SiO₂) with iron-oxide staining, possibly from quartzite, granite, or pegmatite

Travertine (likely polished limestone)

Calcite-rich carbonate rock; predominantly CaCO₃

Weathered limestone or calcareous concretion

Calcite-rich carbonate rock; primarily calcium carbonate (CaCO₃), commonly calcite

Weathered quartz-rich rock, possibly chert or milky quartz

Mostly microcrystalline or crystalline quartz (SiO₂), identification uncertain from photograph

Rounded basalt pebble

Basalt; fine-grained mafic volcanic rock composed mainly of plagioclase and pyroxene, commonly with olivine

River Rock (likely Gneiss or Quartzite)

Metamorphic rock specimen (potentially Foliated Gneiss)

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Quartz (likely) or a Quartzite Pebble

Silicon dioxide (SiO2) for quartz. If it's quartzite, it's a metamorphic rock primarily composed of quartz.

Tiny amber-colored crystal fragment

Indeterminate; possibly quartz, feldspar, mica, or a sulfide mineral

Feldspathic Gneiss

Feldspathic Gneiss (High-grade regional metamorphic rock)