Tektite (Natural Glass)

Quartz Crystal Cluster

Silicon Dioxide (SiO2)

Sandstone

Arenite (composed primarily of SiO2)

Carnelian Agate

SiO2 (Silicon Dioxide - Chalcedony variant)

Quartz Pebble (Feldspathic / Chert Pebble)

Silicon Dioxide (SiO2) / Potassium Feldspar (KAlSi3O8)

Smoky Quartz

Smoky Quartz (Silicon Dioxide - SiO2)

Green Quartz (including Prase or Aventurine variants)

Silicon Dioxide (SiO2) with inclusions (likely Actinolite or Chlorite)

Sandstone

Sandstone (lithified quartz arenite, arkose, graywacke, etc. depending on composition)

Yellow calcite crystal cluster with calcite fragment

Calcite, calcium carbonate (CaCO₃)

Tumbled and polished quartz crystal points

Quartz (silicon dioxide, SiO₂), chiefly rock crystal with smoky or included varieties

Sandstone (with Iron Staining)

Arenite (composed primarily of SiO2 with Fe2O3 staining)

Yellow Quartz (Citrine Quartz or Yellow Chalcedony)

Silicon Dioxide (SiO2)

Speckled rounded stone, likely granite or granitic gneiss

Granite/granitic gneiss; primarily quartz (SiO₂), feldspar, and dark mica or amphibole

Clear Quartz

Silicon Dioxide (SiO2)

White quartz pebble (likely milky quartz)

Quartz, silicon dioxide (SiO₂)

Yellow Quartz or Citrine Geode/Cluster

Silicon Dioxide (SiO2)

Blue Quartzite (Dyed Quartzite)

Quartzite (SiO2 with dye enhancements)

Amethyst Lace Agate / Banded Amethyst

Silicon Dioxide (SiO2) with Fe3+ impurities

Citrine (Heat-Treated Amethyst)

Silicon Dioxide (SiO2)

Yellow Quartz (Citrine/Lemon Quartz)

Silicon Dioxide (SiO2)

Black Onyx or Dyed Agate Node

Cryptocrystalline Quartz (SiO2)

Smoky Quartz on Matrix

Silicon Dioxide (SiO2) with trace impurities and aluminum inclusions

Sandstone (likely Quartzose)

Arenite (primarily SiO2)

Obsidian

Obsidian (volcanic glass, amorphous silica rich rock)

Tumbled carnelian/chalcedony

Carnelian, a reddish variety of microcrystalline quartz (SiO₂)

Milky Quartz Pebble

Quartz (Silicon Dioxide, SiO2)

Sandstone (Pebble)

Sandstone (arenite, arkose, wacke depending on composition)

Tumbled blue chalcedony (likely dyed)

Cryptocrystalline quartz, SiO₂; chalcedony variety

Yellow Quartz (possibly dyed)

Silicon Dioxide (SiO2)

Chert (specifically Blue Chert/Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Weathered granite-like rock

Granite, likely biotite-bearing; exact identification is uncertain from the image

Black Obsidian

Obsidian, volcanic glass (Amorphous SiO₂)

Tumbled milky quartz

Quartz (silicon dioxide, SiO₂)

Quartz with Iron Oxide Stain

Silicon Dioxide (SiO2) with Hematite/Limonite coatings

Pumice

Pumice (Volcanic Rock)

Actinolite (likely fibrous amphibole)

Actinolite, Ca₂(Mg,Fe)₅Si₈O₂₂(OH)₂; possibly an actinolite–tremolite specimen

Amethyst

Amethyst (SiO2 - Silicon Dioxide with iron impurities)

Rhyolite or jasper-bearing volcanic rock

Rhyolite, likely altered and silicified; red coloration may come from hematite

Slag

Anthropogenic Vitreous Silicate / Ferro-silicate Slag

Sandstone

Clastic sedimentary rock (quartz arenite)

Yellow-orange faceted gemstone, likely citrine or yellow topaz

Citrine: quartz, SiO₂; yellow topaz: Al₂SiO₄(F,OH)₂

Clear Quartz

Quartz (Silicon Dioxide, SiO2)

Rose quartz cabochon (probable)

Quartz, silicon dioxide (SiO₂); pink color typically caused by trace elements and microscopic inclusions