Igneous Rock

Schist

Mica Schist (formula variable based on mineral content, typically containing [K,Al,Fe,Mg,Si,O,H])

Obsidian

Volcanic Glass (Amorphous Silicon Dioxide)

Obsidian

Obsidian (Volcanic Glass; SiO2 content > 70%)

Gneiss

Gneiss (High-grade Metamorphic Rock)

Scoria

Vesicular Basalt / Scoria (Mafic volcanic rock)

Gneiss (specifically a weathered or stream-worn specimen)

Gneiss (Foliated Metamorphic Rock)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Amethyst (Chevron or Banded Amethyst)

Silicon Dioxide (SiO2) with iron impurities

Banded Gneiss

Gneiss (High-grade regional metamorphic rock)

Quartz Pebble

Silicon Dioxide (SiO2)

Milky Quartz Pebble

Quartz (Silicon Dioxide, SiO2)

Larimar

Pectolite [NaCa2Si3O8(OH)] with copper substitution

Quartz

Quartz (SiO₂)

Quartz Vein in Host Rock

Silicon Dioxide (SiO2) within Matrix

Granitic Pegmatite (River Rock specimen)

Granite / Pegmatite (composed of SiO2, KAlSi3O8, and NaAlSi3O8)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Milky Quartz

Silicon dioxide (SiO2)

Quartz (likely Rose Quartz or Milky Quartz based on color)

Quartz (SiO2 - Silicon Dioxide)

General Gravel (River Rock/River Stones)

Mixed Lithic Sediments (Conglomerate Clasts)

Biotite Mica

K(Mg,Fe2+)3(Al,Fe3+)Si3O10(OH,F)2

Banded Chalcedony (Agate)

Silicon Dioxide (SiO2) - Cryptocrystalline Quartz

Quartz (specifically Citrine or Yellow Quartzite pebble)

Silicon Dioxide (SiO2)

Milky Quartz (or Iron-Stained Quartz)

Quartz (Silicon Dioxide, SiO2)

Gneiss (specifically Micaceous Gneiss)

Gneiss (High-grade Regional Metamorphic Rock)

Banded Gneiss

Gneiss (Metamorphic high-grade, predominantly SiO2, Al2O3, K2O, Na2O)

Lunar Meteorite (Feldspathic Breccia)

Achondrite, Lunar Meteorite (Feldspathic Breccia)

Porphyritic Basalt (with Quartz or Calcite inclusion)

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

Snowflake Obsidian

Spherulitic Volcanic Glass (primarily SiO2)

Granite

Granite (Mainly Quartz, Feldspar, and Mica)

Obsidian

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

Basalt

Basalt

Granitic Gneiss

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

Greenschist (Chlorite Schist)

Greenschist (containing chlorite, actinolite, and epidote)

Banded Gneiss

Gneiss (High-grade Regional Metamorphic Rock)

Milky Quartz

Quartz (Silicon Dioxide, SiO2)

Granitic Gneiss

Gneiss (High-grade regional metamorphic rock)

Foliated Gneiss (River-Worn Pebble)

Gneiss (High-grade Regional Metamorphic Rock)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Amygdaloidal Basalt

Amygdaloidal Basalt (containing secondary minerals like Quartz, Zeolites, or Calcite)

Orthoclase (Potassium) Feldspar in Quartz

KAlSi3O8 (Potassium Aluminum Silicate)

Brown Antique Granite

Anorthosite (Technically a plutonic rock composed mainly of plagioclase feldspar)

Vesicular Basalt (Scoria)

Extrusive Mafic Volcanic Rock (FeO-SiO2-MgO)