Rock (Likely Sedimentary)

Granite

Phaneritic Felsic Igneous Rock

Chalcedony (Agate Pebble)

Silicon Dioxide (SiO2)

Banded Agate

Cryptocrystalline Quartz (SiO2)

Chert (Jasper/Agate variant)

Microcrystalline Quartz (SiO2) with iron oxide inclusions

Unknown Organic Object (likely a berry or fruit)

Not applicable; this is not a geological specimen. If it were a cranberry, its scientific name would be Vaccinium macrocarpon; if a cherry, it would be Prunus avium or Prunus cerasus.

Rounded river cobble, likely basaltic volcanic rock

Fine-grained mafic igneous rock; likely basalt or andesite

Unakite-like granite with a white feldspar inclusion

Granite, chiefly quartz–feldspar–biotite; pale inclusion likely albite/orthoclase feldspar

Quartz (Milky/Yellowish Pebble)

Silicon Dioxide (SiO2)

Quartz-rich pegmatite (likely granite/pegmatite boulder)

Coarse-grained felsic igneous rock, chiefly quartz (SiO₂), feldspar, and minor mica; exact identification requires testing

Chert (Jasper/Agate mix)

Microcrystalline Quartz (SiO2)

Black river pebble, likely basalt

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

Chert (Jasper variety)

Silicon dioxide (SiO2) - Microcrystalline Quartz

Sandstone

Arenite (primarily SiO2)

Porphyritic Rhyolite

Porphyritic Rhyolite (Extrusive Igneous Rock)

Quartz Pebble

Quartz (Silicon Dioxide, SiO2)

Small dark mineral/rock fragment

Indeterminate; possibly magnetite-bearing basalt or iron-rich slag

Quartz-bearing iron-stained breccia

Brecciated quartz/quartzite with iron oxides, chiefly SiO₂ with hematite/goethite and possible feldspar or host-rock fragments

Basalt cobble

Basalt; fine-grained mafic volcanic rock, chiefly plagioclase and pyroxene

Chert (River Pebble)

Silicon Dioxide (SiO2)

Quartz Vein on Matrix

Silicon Dioxide (SiO2)

Basalt River Pebble

Basalt (Extrusive Igneous Rock)

Granite

Granite (Phaneritic igneous rock)

Banded gneiss, probably granitic gneiss

Foliated gneiss composed mainly of quartz (SiO₂), feldspar—orthoclase/microcline and plagioclase—and dark mica, commonly biotite K(Mg,Fe)₃AlSi₃O₁₀(F,OH)₂

Chert (Common Opal/Jasper variety)

Cryptocrystalline Quartz (SiO2)

Rounded pebble, likely granite or granitic gneiss

Granite: quartz + feldspar + mica; the specimen may be a granitic metamorphic variant

Limestone with Bitumen/Chert

Calcite (CaCO3) containing organic hydrocarbons

Pyrite cluster (iron pyrite)

Pyrite, FeS₂

Quartz Geode

Silicon Dioxide (SiO2)

Pegmatitic granite, possibly potassium-feldspar-rich

Coarse-grained granite; mainly quartz (SiO₂), potassium feldspar (KAlSi₃O₈), plagioclase, and biotite/hornblende

Yellow-brown quartz/chalcedony fragment

Quartz, SiO₂; likely microcrystalline chalcedony with iron-oxide staining

Milky Quartz (with trace inclusions)

Silicon Dioxide (SiO2)

Banded River Pebble (Gneiss or Quartz-Veined Basalt)

Polished River Siltstone or Quartzite Gneiss

Quartzite

Quartzite (SiO2)

Granite (with mafic xenolith)

Phaneritic Felsic Plutonic Rock

Quartz (Smoky/Milky Pebble)

Silicon Dioxide (SiO2)

Weathered granitoid (likely granite or granitic gneiss)

Granite; chiefly quartz, feldspar, and mica (exact identification uncertain from the photo)

Quartzite

Quartzite (primarily SiO2)

Chert (often called Flint or Agate nodule)

Cryptocrystalline Quartz (SiO2)

Blue Chalcedony

Cryptocrystalline Quartz (SiO2)

Likely slag or metallic industrial byproduct

Unidentified iron-rich ferrous slag; possibly magnetite-bearing slag

Porphyritic Basalt

Basalt with Feldspar Phenocrysts

Pumice (likely weathered/water-worn)

Vesicular volcanic glass