Metamorphic (Low Grade)

Red Garnet

Almandine (Fe3Al2(SiO4)3) or Pyrope (Mg3Al2(SiO4)3)

Almandine Garnet

Iron aluminum silicate (Fe3Al2(SiO4)3)

Blue Quartzite

Quartzite (specifically a variety enriched with blue-coloring minerals)

Metamorphic Rock

Moonstone

Adularia or Orthoclase (KAlSi3O8) or Albite (NaAlSi3O8), specifically with lamellar exsolution of albite and orthoclase.

Almandine Garnet

Almandine (Fe3Al2(SiO4)3)

Graphite

Graphite (C)

igneous or metamorphic (base stone); anthropogenic (decoration)

Pet Rock (Man-made Quartzite or Granite Cobble)

Silicon dioxide (SiO2) mixture; commonly composed of Quartz, Feldspar, and Mica

Amethyst

Quartz (Silicon Dioxide with iron impurities), SiO2

metamorphic (man-made / anthropic)

Fired Clay Brick (Anthropic Rock substitute)

Anthropogenic polycrystalline ceramic (predominantly Mullite and Quartz: Al6Si2O13 + SiO2)

Charoite

Charoite (Hydrated silicate of potassium, sodium, calcium, barium and strontium): (K,Sr,Ba)(Na,Ca)2[Si4O10](OH,f)·H2O

Pyrite in Quartz

Iron Sulfide (FeS2) in Silicon Dioxide (SiO2)

Lapis Lazuli

Complex metamorphic rock consisting mainly of Lazurite (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2, Calcite, and Pyrite

Amethyst

Silicon Dioxide with Iron impurities (SiO2)

Smoky Quartz

Silicon Dioxide (SiO2)

Serpentine

Serpentinite (a rock composed primarily of serpentine minerals like antigorite, chrysotile, and lizardite; general formula (Mg, Fe)3Si2O5(OH)4)

Tiger's Eye (variations include Blue or Hawk's Eye)

Silicon Dioxide with Crocidolite inclusions (SiO2)

Metamorphic mineral

Banded Gneiss

Gneiss (typically quartz, feldspar, mica, amphibole composition)

Mineral (Metamorphic pseudomorph)

Tiger's Eye (Polished Point/Tower)

SiO2 (Silicon Dioxide) with included crocidolite fibers

Blue Sapphire

Corundum (Al2O3 - Aluminum Oxide)

Almandine Garnet

Almandine - Fe3Al2(SiO4)3

Apatite

Apatite group mineral (e.g., Fluorapatite - Ca5(PO4)3F, Chlorapatite - Ca5(PO4)3Cl, Hydroxylapatite - Ca5(PO4)3(OH))

Talc

Talc (Mg₃Si₄O₁₀(OH)₂)

Pink Sapphire

Corundum (Al2O3 with trace Chromium and Iron)

Porcelain (Stoneware Ceramic)

Mullite / Silica-glass composite (Al6Si2O13)

metamorphic (man-made)

Aquamarine

Beryl (Be3Al2Si6O18 with iron impurities)

Igneous, Sedimentary, and Metamorphic mix

Crushed Stone / Gravel (Multiple Rock Types)

Lithic fragments (undifferentiated)

Amethyst

Quartz (SiO2) with trace iron impurities

Gneiss

Gneiss (pronounced 'nice')

Metamorphic Rock

Almandine Garnet

Almandine (Fe3Al2Si3O12)

Mineral (specifically a gemstone variety)

Tiger's Eye

Tiger's Eye (a variety of Quartz, SiO₂)

Quartz (Clear Quartz/Rock Crystal)

Silicon Dioxide (SiO2)

Tanzanite

Blue-violet Zoisite (Ca2Al3(SiO4)3(OH))

Banded Gneiss

Gneiss (pronounced 'nice')

Labradorite

(Ca, Na)(Al, Si)4O8 (Plagioclase Feldspar)

Mineral in a matrix (likely quartz or feldspar)

Biotite Mica

K(Mg,Fe)3AlSi3O10(OH)2

Ironstone Concretion (likely)

Goethite/Hematite/Limonite cemented sediment

Sedimentary Rock

Ruby

Corundum (Al2O3 with Chromium traces)

Dendritic Agate

Silicon Dioxide with Manganese or Iron Oxide inclusions (SiO2 + Mn/Fe)

Citrine

Quartz (SiO2) - variety Citrine

Quartz

Quartz (Silicon Dioxide, SiO2)

Amethyst

Quartz variety; chemical formula: SiO₂ (silicon dioxide) with Fe³⁺ impurities