Igneous

Clear Quartz (Faceted Crystal)

Silicon Dioxide (SiO2)

Ruby

Corundum (Al2O3 with chromium trace elements)

Blue Apatite

Ca5(PO4)3(F,Cl,OH)

Black Obsidian

Volcanic Glass (SiO2 with impurities)

Agate

Silicon dioxide (Chalcedony), SiO2

Tumbled Agate

Silicon Dioxide (Chalcedony / Quartz)

Chalcopyrite

CuFeS2 (Copper Iron Sulfide)

Rose Quartz

SiO2 (Silicon Dioxide with trace Titanium, Iron, or Manganese)

Agate

SiO2

Dark igneous rock with white feldspar/quartz patches

Likely porphyritic basalt or andesite; white patches may be plagioclase feldspar or quartz

Weathered igneous pebble, likely basaltic andesite

Fine-grained mafic to intermediate volcanic rock; chiefly plagioclase feldspar, pyroxene, and possibly olivine or magnetite

Porphyritic igneous rock, possibly basaltic-andesite

Porphyritic andesite/basalt; likely plagioclase phenocrysts in a fine mafic groundmass

Weathered igneous rock fragment, possibly granite or granitic gneiss

Indeterminate; likely quartz–feldspar–mica aggregate (granite), possibly foliated gneiss

Granite-like igneous rock

Likely medium-grained granite or granodiorite; quartz–feldspar–mica aggregate

Porphyritic Igneous Rock / Rhyolite Porphyry

Porphyritic volcanic rock

Porphyritic Igneous Rock / Porphyry

Porphyry (Plagioclase/Quartz phenocrysts in a finer-grained groundmass)

Milky Quartz

Silicon Dioxide (SiO2)

Weathered quartz-rich pebble

Milky quartz, SiO₂, possibly quartzite or a quartz-rich granite fragment

Tumbled labradorite

Labradorite, plagioclase feldspar (approximately NaAlSi₃O₈–CaAl₂Si₂O₈)

Granite

Phaneritic Felsic Igneous Rock

Hypersthene

Hypersthene ((Mg,Fe)SiO₃)

Dark, coarse-grained igneous rock (possibly gabbro)

Gabbro, a coarse-grained mafic intrusive rock; identification is tentative from the photo

Coarse-grained dark igneous rock, probably diorite

Diorite (tentative; exact identification requires closer examination)

Weathered igneous rock, likely basaltic lava (uncertain)

Fine-grained mafic volcanic rock, probably basalt; exact identification requires testing

Weathered mafic igneous rock, likely basalt

Basalt (fine-grained mafic volcanic rock; exact identification is uncertain from the image)

Weathered dark igneous rock, likely basalt

Basalt; chiefly plagioclase feldspar, pyroxene, and commonly olivine or magnetite

Dark igneous rock, likely basalt or andesite

Fine-grained mafic to intermediate volcanic rock; commonly plagioclase ± pyroxene, with possible iron-oxide staining

Weathered basalt or dark igneous rock fragment

Likely basalt, a fine-grained mafic volcanic rock; exact identification is uncertain from the image

Dark igneous rock, possibly basalt or gabbro

Basalt–gabbroic rock; chiefly plagioclase feldspar and pyroxene, with possible olivine or iron oxides

Weathered gray igneous rock, likely granite or granodiorite

Granite–granodiorite; mainly quartz, feldspar, and mica

Weathered coarse-grained igneous rock, likely diorite or gabbro

Diorite–gabbro compositional range; chiefly plagioclase feldspar, amphibole/pyroxene, and minor biotite or quartz

Green-speckled igneous rock, likely epidote-bearing basalt or serpentinite

Tentatively epidote-bearing basalt (compositionally uncertain from the image)

Weathered dark igneous rock, likely basalt

Basalt; chiefly plagioclase feldspar and pyroxene, possibly olivine and iron oxides

Coarse-grained igneous rock, likely granite or granodiorite

Granite–granodiorite; chiefly quartz, feldspar, and biotite/hornblende

Dark, coarse-grained igneous rock, likely basalt or gabbro

Basalt (fine-grained) or gabbro (coarse-grained), composed mainly of plagioclase feldspar and pyroxene

Weathered metal-rich igneous rock, likely basalt or komatiitic peridotite

Probable altered mafic–ultramafic rock containing pyroxene/amphibole, olivine, iron oxides, and possible metallic sulfides

Dark igneous rock, likely basalt

Basalt; fine-grained mafic rock dominated by plagioclase and pyroxene, with possible olivine and iron oxides

Dark weathered igneous cobble, likely basalt

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

Polished dark green igneous pebble

Likely gabbro or diabase (dolerite), composed mainly of plagioclase feldspar and pyroxene

Porphyritic Igneous Rock with Iron Oxide Weathering

Weathered Porphyry (containing Quartz, Feldspar, Amphibole/Biotite, and Hematite/Limonite)

Basalt (or similar Mafic Igneous Rock)

Basalt

Probable rough basalt or mafic igneous fragment

Fine-grained basalt, likely plagioclase–pyroxene–olivine aggregate