Mineral, Possibly Rock Fragment Containing A Mineral

Weathered quartz-rich rock, possibly quartzite or granite fragment

Quartzite (SiO₂-dominant) or altered granitoid; uncertain from image

Porphyritic volcanic rock, likely andesite or rhyolite

Porphyritic andesite–rhyolite; chiefly plagioclase, quartz, and altered ferromagnesian minerals in a fine groundmass

Weathered quartz-rich pebble

Quartz (SiO₂), possibly quartzite or quartz-bearing vein rock

Granite

Intrusive Igneous Rock (composed mainly of quartz, alkali feldspar, and plagioclase)

Quartz-rich rock fragment, possibly milky quartz or quartzite

Quartz (SiO₂); probable quartzite if recrystallized sandstone

Vesicular basalt (weathered volcanic rock)

Basalt, chiefly plagioclase feldspar and clinopyroxene with possible olivine and iron oxides

Weathered iron-rich rock, possibly basalt or ironstone

Indeterminate; likely Fe-oxide-bearing basaltic rock (commonly magnetite/hematite in a silicate matrix)

Likely quartz-rich stone, possibly quartzite or milky quartz

Quartz (silicon dioxide, SiO₂); exact rock identification is uncertain from the image

Biotite-rich schist

Mica schist; primarily quartz, feldspar, and biotite mica

Weathered quartz-rich rock fragment

Likely quartz–feldspar-rich granitoid, possibly granite or granitic gneiss; exact identification is uncertain from the image

Small quartz-rich rock fragment (possibly weathered quartz vein material)

Quartz (SiO₂) in an undetermined host rock; the image is insufficient to identify the host confidently

Granite Pebble

Granite (Plutonic Igneous Rock)

Tumbled or naturally etched mica-rich mineral specimen, likely muscovite

Muscovite, KAl₂(AlSi₃O₁₀)(OH)₂; possibly phlogopite mica

Quartz in Matrix (possibly with Biotite or Hornblende)

Quartz (Silicon Dioxide, SiO2) in Granitic Matrix

Tumbled white mineral fragment

Indeterminate; possibly milky quartz or calcite

Tumbled Amethyst

Quartz (Silicon Dioxide, SiO2, colored by iron impurities)

Gabbroic rock, possibly hornblende gabbro

Gabbro; coarse-grained mafic silicate rock dominated by plagioclase and pyroxene, with possible hornblende and magnetite

Ferruginous Sandstone

Sandstone (rich in iron oxides/hydroxides)

Conglomerate

Conglomerate (Detrital sedimentary rock)

Likely basaltic rock

Fine-grained basalt, possibly dolerite/diabase

Sandstone

Arenite (SiO2 + various cementing minerals)

Unidentified gray stone/concrete-like fragment

Indeterminate; likely a fine-grained carbonate or cementitious geological fragment

Weathered granitic rock, possibly granite or granodiorite

Coarse crystalline quartz–feldspar–mica aggregate; commonly granite/granodiorite

Fossiliferous limestone (coral or shell-fragment limestone)

Bioclastic limestone, predominantly calcite (CaCO₃)

Mixed polished rock/mineral specimens

Indeterminate from image; likely quartz-bearing material with iron-oxide staining and possibly mica-rich schist

Red jasper (likely iron-rich chert)

Microcrystalline quartz, SiO₂, colored mainly by hematite/goethite

Quartz-rich pegmatitic rock, possibly rose quartz with mica

Granitic pegmatite; predominantly quartz (SiO₂), with feldspar and mica

Green Aventurine

Aventurine Quartz (SiO2 + Cr-bearing Mica inclusions)

Sodalite

Sodalite, Na₈(Al₆Si₆O₂₄)Cl₂

Weathered fossiliferous limestone

Calcitic limestone, primarily CaCO₃; possibly containing fossil or solution cavities

Weathered vesicular volcanic rock (likely basalt or andesite)

Amygdaloidal basalt/andesite; cavities may contain calcite, zeolites, or silica minerals

Weathered basalt or iron-rich river cobble

Basalt, likely with iron-oxide staining; exact identification requires testing

Weathered quartz-rich pebble

Likely quartz (SiO₂), possibly a small quartzite or feldspathic rock fragment

Red Sandstone

Arenite (primarily Quartz with Hematite cement)

Sandstone (Red Sandstone)

Arenite

Sandstone (Banded Sandstone)

Clastic Sedimentary Rock (primarily SiO2 with iron oxide impurities)

Fossiliferous limestone

Bioclastic limestone, containing a fossil shell or coral fragment

Quartz-rich breccia or pegmatitic granite fragment

Quartz–feldspar rock; possibly hydrothermal quartz breccia

Sandstone

Arenite (composed primarily of SiO2)

Brecciated polymictic rock, possibly impact breccia

Polymictic breccia; exact lithology indeterminate from image

Amethyst-bearing quartz cluster

Quartz, SiO₂; purple coloration commonly from iron-related defects and irradiation

Quartz Geode Fragment

Silicon Dioxide (SiO2)