Igneous Or Sedimentary (Anthropogenic Modification)

Quartz (likely tumbled or naturally water-worn)

Quartz (SiO₂ - Silicon Dioxide)

River Rock (Granitic Gneiss)

Foliated Granitic Gneiss

Quartz (specifically Milky Quartz/Quartzite)

Silicon Dioxide (SiO2)

Folded Schist / Gneiss (Metamorphic Rock)

Regional Metaphoric Folded Outcrop (predominantly Schist/Gneiss)

Veined Quartz

SiO2 (Silicon Dioxide)

Weathered pegmatite or feldspar-rich granite fragment

Granitic pegmatite, composed mainly of potassium feldspar and quartz, with minor mica; exact identification is uncertain from the photograph

Quartz (likely Yellow/Orange variety, possibly Citrine or Chalcedony with iron staining)

Quartz (SiO₂)

Quartz

Quartz (SiO₂)

Black Obsidian and Hematite

Volcanic Glass (SiO2) and Hematite (Fe2O3)

Quartz-bearing metamorphic rock, likely garnet-mica schist

Quartz–mica schist with probable garnet and iron-oxide minerals

Quartz on Matrix

Silicon Dioxide (SiO2)

Blue Apatite

Fluorapatite (Ca5(PO4)3F)

Pyrite

Iron Sulfide (FeS2)

Fluorite

Fluorite (Calcium Fluoride, CaF2)

Quartz (Milky Quartz)

Silicon Dioxide (SiO2)

Carnelian Agate

Carnelian (Silicon Dioxide: SiO2) with iron oxide impurities

Terracotta (Man-made ceramic brick fragment)

Baked clay / High-iron ceramic (Silicate-based ceramic)

Mixed river-worn rock and mineral collection

Mostly quartz/quartzite, feldspar-bearing granitoid, chert, and mafic volcanic rocks; exact species vary by pebble

Quartz-bearing rock or quartz-rich mineral specimen

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

Hematite

Iron(III) oxide (Fe2O3)

Quartz (Milky Quartz)

Silicon Dioxide (SiO2)

Hematite

Iron(III) oxide (Fe2O3)

Gneiss

Gneiss

Pyrite (Fool's Gold)

Iron Disulfide (FeS2)

Gneiss

Gneiss (High-grade Regional Metamorphic Rock)

Garnet (likely Almandine or a blend)

Garnet group: X3Y2(SiO4)3, where X can be Ca, Mg, Fe2+, Mn2+ and Y can be Al, Fe3+, Cr3+. Given the dark, somewhat reddish-brown appearance in the image, it's likely Almandine (Fe3Al2(SiO4)3) or a mix with other iron-rich garnets.

Garnet (Red Garnet)

Garnet Group. The red varieties seen in jewelry are typically Almandine (Fe3Al2(SiO4)3), Pyrope (Mg3Al2(SiO4)3), or a mix of the two (pyrope-almandine series).

Concrete with Aggregate

Composite construction material; primary matrix is Calcium Silicate Hydrate (C-S-H)

Quartz (likely Milky Quartz)

Quartz (SiO₂ - Silicon Dioxide)

Quartz Pebble

Silicon Dioxide (SiO2)

Clear Quartz Cluster

Crystalline Silicon Dioxide (SiO2)

Gneiss

Gneiss (quartz-feldspar-biotite gneiss)

Banded Agate (specifically Botryoidal/Orbicular Agate)

Silicon Dioxide (SiO2)

Pyrite (Fool's Gold)

Iron Disulfide (FeS2)

Milky Quartz

Quartz (Silicon Dioxide, SiO2)

Quartz (Milky Quartz)

Quartz (SiO2 - Silicon Dioxide)

Green Fluorite

Calcium Fluoride (CaF2)

Milky Quartz

Crystalline Silicon Dioxide (SiO2)

Smoky Quartz with Chert

Silicon Dioxide (SiO2)

Fluorite

Calcium Fluoride (CaF2)

Banded Gneiss

Gneiss (High-grade Regional Metamorphic Rock)

Granitic Gneiss

Gneiss (high-grade metamorphic rock primarily of quartz, feldspar, and mica)