Rock

Polished brecciated jasper

Jasper, an opaque microcrystalline variety of chalcedony (SiO₂), with iron-oxide staining

Sandstone (with Iron Staining)

Arenite (primarily SiO2 with Fe2O3/FeO(OH) oxides)

Sandstone (with potentially high Feldspar/Arkose content)

Clastic sedimentary rock (SiO2 dominated)

Sandstone

Arenite

Quartz-rich geode or mineralized cavity in host rock

Likely a quartz-bearing geode; the pale crystals may be quartz (SiO₂), but the photo is not detailed enough for a firm identification.

Smooth river pebble

Indeterminate lithology; likely fine-grained quartz-rich sandstone, siltstone, or weathered chert

Quartz (Druzy)

Silicon Dioxide (SiO2)

Likely garnet-bearing metamorphic rock

Garnet-bearing schist or gneiss; the visible dark crystal may be almandine garnet (Fe₃Al₂(SiO₄)₃)

Granite pebble

Granite, chiefly quartz, feldspar, and mica

Weathered granite or granitic gneiss

Granitic rock, chiefly quartz, feldspar, and mica; exact identification is uncertain from the photograph

Weathered granite or granitic gneiss block

Granite, chiefly quartz, feldspar, and mica; possibly gneiss if the visible banding is structural

Rounded granitic pebble

Granite, likely biotite granite or granodiorite

Iron-stained quartz-rich rock (possibly ironstone or ochre-coated quartz)

Undetermined ferruginous rock; yellow-brown coloration likely from goethite and/or limonite (hydrated iron oxides)

Weathered granite

Granite, a coarse-grained felsic intrusive igneous rock composed mainly of quartz, feldspars, and mica

Ironstone Concretion (Ironstone Gourd)

Limonite/Goethite Concretion (FeOO(H))

Gneiss (Metamorphic Pebble)

Gneissic Metamorphic Rock

Weathered iron-rich rock (possibly ironstone)

Indeterminate ferruginous rock; likely iron-oxide-cemented sandstone or ironstone

Unknown Rock Fragment

Unknown

River Rock / Stream Pebble

Fluvial Clast / Rounded Sedimentary Particle

Vuggy Quartz on Matrix

Crystalline Silicon Dioxide (SiO2)

Quartzite pebble

Quartzite (mostly SiO2)

Generic Rock Fragment

Rock Fragment

Sandstone

Clastic sedimentary rock (primarily SiO2)

Basalt with Quartz Veins

Basalt (with SiO2 veins)

Sandstone

Arenite (primarily SiO2)

Basalt

Extrusive Igneous Rock

Basalt

Mafic Igneous Rock (composed primarily of pyroxene and calcium-rich plagioclase)

Shale

Argillaceous Rock

Banded gneiss

Foliated gneiss, likely quartz–feldspar–biotite gneiss

Sandstone

Arenite (primarily SiO2)

Weathered quartz-rich rock, possibly granite or quartzite

Indeterminate; likely quartz–feldspar aggregate, possibly granitic gneiss

Small dark stone (unidentified)

Undetermined; image lacks enough detail for reliable identification

Asphalt aggregate pavement

Bituminous asphalt concrete containing crushed stone aggregate

Gneiss Pebble

Gneiss

Vesicular Basalt with Quartz/Chalcedony

Vesicular Basalt (primarily Plagioclase, Pyroxene, and Olivine with SiO2 infill)

Chert (River Pebble)

Microcrystalline Quartz (SiO2)

Basalt

Vesicular Basalt

Granite Core Sample

Granite

Shale

Shale (Fine-grained clastic sedimentary rock)

Quartzite with Schist layers

Metamorphosed Quartz-rich Rock (Mixed Schist/Quartzite)

Milky Quartz

Silicon Dioxide (SiO2)

Dalmation Jasper

Aplite with Arfvedsonite inclusions (SiO2 with Na3(Mg,Fe2+)4AlSi8O22(OH)2)