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

Fossiliferous Limestone (Coquina)

Biogenic Limestone (Calcium Carbonate, CaCO3)

Lapis Lazuli

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

Blue Calcite

Calcium Carbonate (CaCO3)

Chert (Jasper/Agate variety)

Microcrystalline Quartz (SiO2)

Marble

Crystalline Limestone (mostly CaCO3 / Calcium Carbonate)

Chert (Gravel pebble)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Lapis Lazuli (Raw)

Lazurite-rich metamorphic rock; Na3Ca(Al3Si3O12)S

Quartzite

Quartzite

Tiffany Stone

Fluoritized Opal Beryllium Ore (principally Bertrandite, Be4Si2O7(OH)2)

Chevron Amethyst

SiO2 (Quartz with Manganese/Iron impurities)

Quartz Geode

Silicon Dioxide (SiO2)

Fossiliferous Limestone with Rugose Coral

Calcium Carbonate (CaCO3) featuring Rugosa (extinct order of solitary and colony corals)

Limestone

Calcium Carbonate (CaCO3)

Chert / Flint

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Amethyst

Amethyst (Silicon Dioxide, SiO2 with Iron impurities)

Chert (Flint)

Microcrystalline Quartz (SiO2)

Chert (Jasper/Flint variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Quartz Vein in River Siltstone

Crystalline Quartz (SiO2) in Siliclastic Matrix

Fluorite (Rainbow Fluorite)

Fluorite (Calcium Fluoride, CaF2)

Amethyst

Silicon Dioxide (SiO2) with iron impurities

Calcite

Calcium Carbonate (CaCO3)

Fossil Coral

Scleractinia (fossilized calcium carbonate)

Marble (polished)

Recrystallized Calcite (CaCO3)

Pink Stained Rock (Likely Quartzite or Sandstone with Iron Oxide Staining)

Quartzite (metamorphic) or Sandstone (sedimentary); coloration likely due to hematite or other iron oxides.

Chert (Nodule)

Microcrystalline or Cryptocrystalline Silica (SiO2)

Rough Amethyst

Silicon Dioxide (SiO2) with Iron impurities

Microcrystalline Limestone Pebble

Carbonate sedimentary rock (Calcium Carbonate, CaCO3)

Chert (Iron-stained)

Microcrystalline Quartz (SiO2)

Chert (Common Opal/Chalcedony)

Microcrystalline Quartz (SiO2)

Quartz

Quartz (SiO₂)

Quartzite Pebble

Quartzite (primarily SiO2)

Chert (Jasper-bearing)

Chert (Silicon Dioxide, SiO2)

Agate (Common Chalcedony)

Silicon Dioxide (SiO2)

Amethyst

Amethyst (Silicon Dioxide, SiO2)

Amethyst

Silicon Dioxide (SiO2) with Iron impurities

Chert (Arrowhead variety)

Chert (SiO2)

Amethyst Geode

Amethyst (Silicon Dioxide), Formula: SiO2

Amethyst

Silicon Dioxide (SiO2) with iron impurities

Amethyst

Amethyst (Silicon Dioxide, SiO2)

Agate Geode with Quartz Druzy

Chalcedony (SiO2) and Quartz (SiO2)

Quartzite Pebble (River Rock)

Quartzite (primarily SiO2)

Lapis Lazuli

Lapis Lazuli (a rock composed primarily of Lazurite)