Igneous Rock (Volcanic Glass)

Limonite-stained Quartz

Silicon Dioxide (SiO2) with Iron Oxide/Hydroxide (FeO(OH)·nH2O) staining

Amethyst (Chevron or Banded Amethyst)

Silicon Dioxide (SiO2) with iron impurities

Milky Quartz (with Iron Oxide staining)

Silicon Dioxide (SiO2)

Porphyritic Basalt (with Quartz or Calcite inclusion)

Porphyritic Basalt (Matrix: SiO2/MgO/FeO, Phenocryst: likely Quartz or Calcite)

Milky Quartz

Silicon Dioxide (SiO2)

Quartz (Milky/Smoky variety)

Silicon Dioxide (SiO2)

Rough Corundum (likely Sapphire/Zircon-bearing)

Aluminium Oxide (Al2O3)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Bull Quartz

Quartz (Silicon Dioxide - SiO2)

Amethyst

Silicon Dioxide (SiO2) with iron impurities

Smoky Quartz

Silicon Dioxide (SiO2) with aluminum impurities

Black Obsidian

Volcanic Glass (Amorphous Silicon Dioxide SiO2)

Clear Quartz

Silicon Dioxide (SiO2)

Quartz Vein in Gneiss or Basalt

Milky Quartz (SiO2) within Metamorphic Host Rock

Granitic Pegmatite

Granitic Pegmatite with Quartz and Feldspar

Pink Granite

Phaneritic Igneous Rock (high K-feldspar content)

Red Jasper

Jasper (Silicon Dioxide based crypto-crystalline Quartz with Iron inclusions)

Tektite (Indochinite)

Tektite (impactite), primarily high-silica glass (SiO2)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Milky Quartz Pebble

Crystalline Silicon Dioxide (SiO2)

Basalt

Basalt

Quartz / Milky Quartz

Silicon Dioxide (SiO2)

Snowflake Obsidian

Vitreous volcanic silicate (SiO2 with Cristobalite inclusions)

Milky Quartz with Mineral Inclusions

Quartz (Silicon Dioxide, SiO2)

Drupa Quartz (Sparkly Drusy Quartz on Matrix)

Crystalline Silicon Dioxide (SiO2) on host rock

Quartz (likely Milky Quartz or Chalcedony)

Quartz (SiO2 - Silicon Dioxide)

Obsidian (Black Obsidian)

Volcanic Glass (Primary composition: SiO2 - Silicon Dioxide)

Scoria

Vesicular Basaltic Glass (comprised primarily of volcanic glass/silica with plagioclase, pyroxene, and olivine crystals)

Quartz (specifically Milky/Gray Quartz)

Silicon Dioxide (SiO2)

Obsidian

Obsidian (Volcanic Glass), primarily SiO2 (Silicon Dioxide)

Snowflake Obsidian

Spherulitic Obsidian (SiO2 + impurities)

Druzy Quartz

Quartz (Silicon Dioxide, SiO2)

White Topaz

Aluminum Silicate Fluoride Hydroxide; Al2SiO4(F,OH)2

Gold Sheen Obsidian

Volcanic Glass (SiO2 + Fe3O4 / Gas Inclusions)

Banded Agate (specifically Moss or River Agate variety)

Cryptocrystalline Quartz (SiO2)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Jasper

Silicon Dioxide (SiO2)

Quartz (Rose or Clear variety)

Silicon Dioxide (SiO2)

Milky Quartz

Silicon Dioxide (SiO2)

Milky Quartz

Silicon Dioxide (SiO2)

Amethyst

Silicon dioxide (SiO2) with iron impurities

Pink Granite

Phaneritic plutonic igneous rock (Alkali-feldspar granite)