Not A Rock Or Mineral

Metal Alloy (Likely Pewter or Sterling Silver)

Not a natural geological specimen; composed of refined metals. If pewter, it's a tin-based alloy. If sterling silver, it's 92.5% silver and 7.5% other metals (usually copper).

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Gneiss

Gneiss (a rock type, not a specific mineral with a formula)

Biological Bone (Patella/Knee)

Patella (part of the Human Skeletal System)

Vesicular basalt (possibly gold-bearing or mineral-veined basalt)

Basalt, a mafic volcanic rock composed chiefly of plagioclase feldspar, clinopyroxene, and often olivine

Pumice

Pumice (volcanic rock)

N/A - Non-Geological Item

Serpentine

Serpentinite (a rock composed primarily of serpentine minerals like antigorite, chrysotile, and lizardite; general formula (Mg, Fe)3Si2O5(OH)4)

Copper Ore / Altered Granodiorite

Cupriferous rock with silicate gangue

Honey-colored chalcedony (possibly yellow/orange agate or carnelian)

Chalcedony, a microcrystalline variety of quartz; SiO₂. The color may result from iron-oxide inclusions. Exact identification is uncertain from a photograph alone.

Granite

Granite, a coarse-grained felsic intrusive igneous rock composed chiefly of quartz, feldspar, and mica or amphibole

Granite

Granite (a felsic intrusive igneous rock)

Granite

Intrusive Igneous Rock

Likely banded gneiss

Quartz–feldspar–mica gneiss (tentative visual identification)

Angular gray rock fragments

Unidentified fine-grained rock; the image does not show diagnostic features sufficient for a specific identification

Likely greenstone (chlorite/epidote-altered basalt), waterworn pebble

Greenschist-facies metabasalt; commonly composed of chlorite, actinolite, epidote, and albite

Basalt with Quartz Vein

Mafic volcanic rock with hydrothermal SiO2 filling

Digital Multimeter (Synthetic Object)

Digital Multimeter (DMM)

Likely altered volcanic rock (greenstone)

Chlorite–epidote–actinolite-rich metavolcanic rock; exact identification requires testing

Vein Quartz in Basalt

Silicate-veined volcanic rock

Granite (weathered cobble)

Granite; chiefly quartz, feldspar, and mica/amphibole

Granite (small weathered fragment)

Granite, composed chiefly of quartz, feldspar, and mica

Granite pebble

Granite, chiefly quartz, feldspar, and mica

Likely granite pebble

Granite, a quartz–feldspar–mica intrusive igneous rock

Rock Specimen

Unclassified rock specimen

Crushed stone aggregate

Mixed lithic aggregate; individual fragments cannot be identified from the image

Banded gneiss

Foliated gneiss, likely quartz–feldspar–biotite gneiss

Granite boulder

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

Likely weathered granite or granitic gneiss

Granite: quartz, feldspar, and mica; exact identification is uncertain from the image

Gravel / Crushed Stone

Aggregate (mixed mineral rock fragments)

Serpentine

Serpentine subgroup (Mg,Fe)3Si2O5(OH)4

Serpentine

(Mg,Fe)3Si2O5(OH)4

Greenstone pebble (possibly altered basalt)

Chlorite- and/or epidote-altered basalt; exact identification requires testing

Rough garnet-bearing rock, likely almandine garnet in matrix

Almandine garnet, Fe₃Al₂(SiO₄)₃; exact host rock cannot be determined from the image

Polished greenstone pebble

Likely chlorite- or actinolite-bearing greenstone (metamorphosed mafic rock)

Gneiss (rounded cobble)

Quartz–feldspar–mica gneiss; exact mineral proportions cannot be determined from the image

Granite

Granite (a common rock name, not a single mineral species, composed primarily of quartz, feldspar, and mica/amphibole)

Milky Quartz Pebble with Iron Inclusions

Silicon Dioxide (SiO2)

Red Granite

Granite

Granite (likely biotite-bearing granite)

Granite, composed mainly of quartz, feldspar, and mica (likely biotite)

Red Sandstone

Clastic Sandstone (typically Quartz-rich with Iron Oxide)

Granite

Felsic intrusive igneous rock