Crystal

Herkimer Diamond

Quartz (Silicon Dioxide, SiO2)

Quartz Crystal (specifically a Double-Terminated variety)

Silicon Dioxide (SiO2) - Low Quartz

Amethyst

Quartz (Silicon Dioxide) SiO2 with iron impurities

Amethyst

Silicon Dioxide (SiO2) with iron impurities

Green tourmaline crystal (probable)

Elbaite tourmaline, complex borosilicate; approximate formula Na(Li,Al)₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

Iron-rich quartz crystal

Quartz, SiO₂, likely iron-stained or hematite-included quartz

Tumbled quartz crystal (probable)

Quartz, silicon dioxide (SiO₂)

Tumbled quartz (rock crystal)

Quartz, silicon dioxide (SiO₂)

Rough green tourmaline crystal

Elbaite tourmaline, complex sodium-lithium aluminum borosilicate; approximate formula Na(Li,Al)₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

Milky quartz (quartz crystal)

Quartz, silicon dioxide (SiO₂)

Green tourmaline crystal (likely elbaite)

Elbaite tourmaline, a complex borosilicate: Na(Li,Al)₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

Quartz Geode

Crystalline Silicon Dioxide (SiO2) in Geode

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Pyromorphite on Epidote

Pyromorphite [Pb5(PO4)3Cl] and Epidote [Ca2(Al2,Fe3+)(SiO4)3(OH)]

Obsidian

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

Desert Rose Selenite (Gypsum)

Gypsum (Calcium Sulfate Dihydrate) - CaSO4·2H2O

Amethyst Quartz Druse

Silicon Dioxide (SiO2) with iron impurities

Obsidian

Volcanic Glass (Amorphous Silicon Dioxide)

Rose Quartz

Silicon Dioxide (SiO2)

Amethyst (Scepter Quartz)

Silicon Dioxide (SiO2) with Iron impurities

Clear quartz (likely quartz crystal fragment)

Quartz, silicon dioxide (SiO₂)

Milky quartz (rough quartz crystal)

Quartz, silicon dioxide (SiO₂)

Pyrite in Matrix (Quartz/Schist)

Iron Sulfide (FeS2)

Quartz crystal (likely citrine or iron-stained quartz)

Quartz, silicon dioxide (SiO₂)

Clear Quartz Crystal

Silicon Dioxide (SiO2)

Quartz (Crystal Cluster)

Silicon Dioxide (SiO2)

Amethyst cluster

Quartz, SiO₂, violet variety (amethyst)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Snowflake Obsidian

Obsidian with Cristobalite inclusions

Obsidian

Volcanic Glass (SiO2 rich)

Snowflake Obsidian

Hydrated Volcanic Glass (primarily SiO2) with Cristobalite inclusions

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Quartz Geode (Smoky Quartz)

Silicon Dioxide (SiO2)

Small clear crystal, possibly quartz or glass-like gemstone

Uncertain; likely quartz (SiO₂), but the image is insufficient to exclude man-made glass or cubic zirconia

Amethyst and Milky Quartz

Silicon Dioxide (SiO2)

Clear quartz crystal (likely)

Quartz, silicon dioxide (SiO₂)