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

Agatized Chert / Chalcedony

Silicon Dioxide (SiO2)

Quartz Geode in Sedimentary Matrix

Silicon Dioxide (SiO2) within a limestone/dolostone host

Fossiliferous Limestone (Crinoidal Limestone)

Biogenic Limestone (Calcium Carbonate, CaCO3)

Marble (White)

Metamorphosed Limestone (mainly CaCO3)

Quartzite

Quartzite (SiO2)

Quartzite (specifically a river-worn cobble)

Quartzite (primarily Silicon Dioxide, SiO2)

Amethyst

Crystalline Quartz (SiO2) with iron impurities

Chert (varietal: Flint Pitted Pebble)

Cryptocrystalline Quartz (SiO2)

Chalcedony Nodule (Agate/Chert)

Chalcedony (cryptocrystalline Silicon Dioxide, SiO2)

Quartz Geode/Druzy Quartz

Quartz (SiO₂)

Chert Concretion (with typical hematite/limonite staining)

Sedimentary Concretion (SiO2 with FeO(OH)⋅nH2O)

Chert (Field Stone/Pebble)

Microcrystalline or cryptocrystalline Quartz (SiO2)

Marble

Marble (metamorphosed limestone or dolostone), primarily composed of calcite (CaCO3) or dolomite (CaMg(CO3)2)

Limestone (specifically Chalky Limestone)

Calcium Carbonate (CaCO3 / Calcite)

Marble

Recrystallized Calcite (CaCO3)

Blue Calcite

Calcium Carbonate (CaCO3)

Quartz (Drusy/Crystalline)

Silicon Dioxide (SiO2)

Geode (Chert or Quartz Nodule)

Silicon Dioxide (SiO2)

Amethyst (Tumbled/Polished)

Silicon Dioxide (SiO2) with iron impurities

Chert (Nodule / Geode fragment)

Microcrystalline Quartz (SiO2)

Blue Apatite

Apatite-(CaF), Ca5(PO4)3F

Marble

Metamorphic rock composed of Recrystallized Carbonate Minerals (chiefly CaCO3)

Agate (Polished Slice)

Banded Chalcedony (SiO2)

Quartz Geode

Silicon Dioxide (SiO2)

Oolitic Limestone

Oolite (Sedimentary rock composed of CaCO3)

White Calcite

Calcium Carbonate (CaCO3)

Amethyst

Silicon Dioxide (SiO2) with traces of Iron and Manganese

Sandstone (Quartzose Sandstone)

Clastic Terrigenous Sedimentary Rock (primarily SiO2)

Amethyst (Pale/Light Variety)

Quartz (Silicon Dioxide) with Iron impurities - SiO2

Sandstone Geode (Unbroken)

Siliciclastic sedimentary rock (primarily Quartz)

Citrine Geode

Citrine (Silicon Dioxide, SiO2)

Crushed Limestone

Sedimentary Carbonate Rock (CaCO3)

Orange Calcite

Calcite (Calcium Carbonate, CaCO3)

Marble

Metamorphosed Limestone (mainly CaCO3)

Quartz Geode

Quartz (Silicon Dioxide, SiO2) Geode

Yellow Calcite

Calcium Carbonate (CaCO3)

Seashell Fragment (Aragonite/Calcite)

Calcium Carbonate (CaCO3) - Shell fragment

Amethyst

Amethyst (Silicon Dioxide with iron impurities), SiO2

Quartzite (Potentially Ferruginous)

Quartzite (SiO2)

Lapis Lazuli

Lapis Lazuli (Complex silicate rock containing Lazurite (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2, Calcite, and Pyrite)

Amethyst

Silicon Dioxide (SiO2) with iron impurities

Dyed Agate (Tumbled)

Silicon Dioxide (SiO2) - Microcrystalline Quartz