The Purple Specimen Is A Mineral (Amethyst); The White Specimen Is A Sedimentary Rock (Limestone Or Marble).

Chert (Septarian Nodules / Weathered Silex)

Microcrystalline Quartz (SiO2)

Black Marble

Recrystallized Carbonate Rock (CaCO3)

Green Onyx (Banded Calcite)

Travertine (CaCO3 - Calcium Carbonate)

Chalcedony (Botryoidal or Geode form)

Silicon Dioxide (SiO2)

Banded Calcite (Mexican Onyx)

Calcium Carbonate (CaCO3)

Chert (with Quartz vein)

Chert (Silicon Dioxide, SiO2)

Geode (Unopened)

Silica-lined Vug (primarily SiO2)

Chert (Flint)

Chert (SiO2)

Lapis Lazuli (Low Grade)

Lazurite-rich metamorphic rock ((Na,Ca)8(AlSiO4)6(SO4,S,Cl,OH)2)

Amethyst

Amethyst (SiO₂)

Geode with Iron-Stained Quartz/Calcite

Silicon Dioxide (SiO2) or Calcium Carbonate (CaCO3) in Sedimentary Matrix

Banded Sandstone

Arenite (composed primarily of Quartz: SiO2)

Crazy Lace Agate

Chalcedony (Silicon Dioxide, SiO2)

Marble (White)

Recrystallized Calcite (CaCO3) or Dolomite (CaMg(CO3)2)

Lapis Lazuli

Complex mixture of minerals (lazurite, calcite, pyrite, and sodalite); (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2

Calcite

Calcium Carbonate (CaCO3)

Green Calcite

Calcium Carbonate (CaCO3)

Dendritic Agate (Tree Agate)

Chalcedony (Silicon Dioxide, SiO2) with Manganese or Iron Oxide inclusions

Calcite

Calcite (Calcium Carbonate, CaCO3)

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Pyrite Geode (Sparkling Druzy)

Iron Sulfide (FeS2) in Sedimentary Nodule

Chert (Jasper/Flint variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Lapis Lazuli

Lazurite-rich metamorphic rock

Amethyst (Tumbled)

Silicon Dioxide (SiO2) with iron impurities

Chert (Flint variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert (Common Opal/Chalcedony mixture)

Silicon Dioxide (SiO2)

Amethyst

Silicon Dioxide (SiO2) with iron impurities

Sandstone

Arenite (primarily SiO2)

Quartz (likely milky quartz or a stained variety)

Silicon Dioxide (SiO₂)

Chert (Flint variety)

Chert (SiO2)

Chert (Iron-stained)

Chert (SiO2)

Quartzite

Quartzite (SiO2)

Quartz Geode

Silicon Dioxide (SiO2)

Marble

Recrystallized Calcite (CaCO3)

Limestone with Chert or Siltstone bands

Sedimentary carbonate rock (CaCO3) often with siliceous impurities

Celestine (or Celestite) on Matrix

Celestine (SrSO4)

Amethyst

Amethyst (SiO2 - Silicon Dioxide with iron impurities)

Lapis Lazuli (polished cabochon)

Lazurite-rich metamorphic rock (approx. Na6Ca2Al6Si6O24(SO4,S,Cl)2)

Citrine Quartz

Silicon Dioxide (SiO2)

Banded Calcite (often sold as Yellow Aragonite or Onyx)

Calcium Carbonate (CaCO3)

Chert (Jasper variety) with Iron Oxide staining

Cryptocrystalline Quartz (SiO2) with Goethite/Limonite impurities

Amethyst

Amethyst (Silicon Dioxide, SiO2)