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

Chalcedony (Agatized Coral / Rough Chalcedony Node)

Silicon Dioxide (SiO2)

Chert (including varieties like Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Sandstone (Ferruginous)

Arenite (primarily SiO2 with Fe2O3 staining)

Sandstone (likely with Quartz Veining)

Arenite (primarily SiO2)

Barite Rose on Marcasite

Barium Sulfate (BaSO4) on Iron Sulfide (FeS2)

Jasper

Jasper (Silicon Dioxide, SiO2)

Yellow Quartzite (River Cobble)

Quartzite (mainly SiO2)

Agate with Druzy Quartz

Silicon Dioxide (SiO2)

Chert (Jasper variety)

Silicon Dioxide (SiO2)

Chert (or Chalcedony)

Chert (Microcrystalline Quartz, SiO2)

Limestone with Calcite Veins

Sedimentary Calcium Carbonate (CaCO3)

Ferruginous Sandstone

Arenite with Iron-Oxide Cement (FeO(OH)·nH2O / Fe2O3)

Quartz Geode

Silicon Dioxide (SiO2)

Zebra Jasper (Zebra Stone)

Tumbled Silicon Dioxide (SiO2) with impurities

Chert Breccia

Brecciated Chert (Microcrystalline Silica)

Quartzite Pebble

Metamorphosed Quartz Sandstone (SiO2)

Moonstone

Orthoclase Feldspar (KAlSi3O8)

Prasiolite (Green Quartz)

Silicon Dioxide (SiO2) with iron impurities

Sandstone (Ferruginous)

Arenite with Iron-oxide inclusions (SiO2 primarily)

Amethyst

Silicon Dioxide (SiO2) containing iron impurities

Sandstone (likely Calcareous or Quartz-rich)

Arenite (SiO2 based typically)

Sandstone Pebble

Arenite (primarily SiO2)

Sandstone (with Iron Staining)

Clastic sedimentary rock (primarily Quartz - SiO2)

Chert (Cherty Limestone or Flint)

Microcrystalline Silica (SiO2)

Coquina

Biogenic Limestone (Calcite, CaCO3)

Quartz Geode

Silicon Dioxide (SiO2)

Gneiss (with Quartzite and Biotite)

Gneiss containing SiO2 (Quartz), K(Mg,Fe)3AlSi3O10(OH)2 (Biotite), and (K,Na,Ca)AlSi3O8 (Feldspar)

Sandstone (Ferruginous)

Arenite (primarily SiO2 with Iron Oxide cement)

Coarse-Grained Marble

Recrystallized Limestone (Major component: CaCO3)

Pyrite (on Shale/Matrix)

Iron Disulfide (FeS2)

Almandine Garnet in Matrix

Almandine (Fe3Al2(SiO4)3)

Quartz Crystal Cluster

Silicon Dioxide (SiO2)

Marble (Calcitic)

Metamorphosed Limestone (CaCO3)

Flagstone (Sandstone)

Clastic Sedimentary Rock (composed of quartz and feldspar)

Sandstone (Micaceous)

Arenite (composed primarily of SiO2)

Sandstone Pebble

Arenite (primarily SiO2)

Amethyst (Chevron or Dream Amethyst variety)

Tectosilicate Silicon Dioxide (SiO2) with iron impurities

Sandstone (Ferruginous)

Arenite (primarily SiO2 with Fe2O3 staining)

Sandstone (Weathered Pebble)

Arenite (SiO2 primarily)

Sandstone Pebble

Arenite (primarily Quartz, SiO2)

Sandstone (Glacial Cobble)

Arenite / Sedimentary Rock (primarily SiO2)

Quartz Vein in Host Rock

Silicon Dioxide (SiO2) within Sedimentary or Igneous Matrix