Manufactured Glass

Black Onyx

Chalcedony (Silicon Dioxide, SiO2)

Yellow Quartz (or Citrine Quartz)

Silicon Dioxide (SiO2)

Green Fluorite

Fluorite (Calcium Fluoride - CaF2)

Slag Glass

Vitreous Silicate Residue

Sea Glass

Amorphous Silica (Anthropogenic glass) - SiO2

Slag Glass

Glassy Silicate Residue

Amethyst

Amethyst (Silicon Dioxide - SiO2)

Clear Quartz Sphere

Silicon Dioxide (SiO2)

Chert (specifically Jasper or Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Sandstone

Sandstone (arenite is a more specific geological term for a clean sandstone, while wacke refers to a dirty sandstone with significant matrix)

Snowflake Obsidian

Volcanic glass containing Spherulites (SiO2)

Snowflake Obsidian

Volcanic Glass with Spherulite Inclusions (70-75% SiO2)

Fulgurite

Liesegang (Fulgurite)

Artisanal Glass Beads (Simulated Goldstone or Aventurine Glass)

Silicon Dioxide (SiO2) with metallic inclusions

Sea Glass (often mistaken for Gemstones)

Amorphous Silica (SiO2) with trace additives

Milky Quartz

Quartz (Silicon Dioxide, SiO2)

Moss Agate

Chalcedony (Silicon Dioxide, SiO2) with inclusions

Silicon

Silicon (Si)

Blue Kyanite

Kyanite (Al2SiO5)

Kyanite

Kyanite (Al2SiO5)

Iron Ore / Ironstone Concretion

Mixture of iron oxide/hydroxide minerals, likely some combination of Hematite (Fe2O3), Goethite (α-FeOOH), and Limonite (a general term for hydrated iron oxides of variable composition) or potentially Bauxite (a mixture of aluminum hydroxides, often with iron oxides, (Al(OH)3) and FeO(OH)). The visual characteristics strongly suggest iron-rich material.

Mica Schist

Mica Schist (predominantly Muscovite or Biotite sheet silicates)

Red Jasper

Jasper (Silicon Dioxide, SiO2)

Chert / Flint Nodule

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Red Jasper

Jasper (Silicate Mineral), SiO2 with Fe2O3 inclusions

Chert (often called Flint when dark)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Sandstone (with Iron Staining)

Clastic sedimentary rock (primarily Quartz with Limonite/Goethite staining)

Sandstone

Arenite (composed primarily of SiO2)

Muscovite Mica

Muscovite (Potassium Aluminum Silicate Hydroxide Fluoride), KAl2(AlSi3O10)(OH,F)2

Snowflake Obsidian

Hydrated Volcanic Glass (primarily SiO2) with Cristobalite inclusions

Obsidian

Amorphous volcanic glass (SiO2)

Pumice

Pumice (Amorphous volcanic glass)

Libyan Desert Glass

Impactite silica glass (SiO2)

Obsidian

Extrusive igneous volcanic glass (rich in SiO2)

Rose Quartz

Silicon Dioxide (SiO2) with trace amounts of titanium, iron, or manganese

Quartzite (River Stone)

Quartzite

Quartzite

Quartzite (SiO2)

Aventurine

Silicon Dioxide (Quartz with Fuchsite inclusions) - SiO2

Tektite (Indochinite)

Tektite - High-silica amorphous glass (SiO2 + Al2O3)

Libyan Desert Glass

Impactite (High-silica tektite)

Smoky Quartz

Silicon Dioxide (SiO2)

Pumice (Volcanic Rock)

Vesicular volcanic rock (composed largely of amorphous volcanic glass)