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

Chert (Yellow Jasper/Flint)

Microcrystalline Quartz (SiO2)

Calcite

Calcite (CaCO3)

Chert (often found as Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Amethyst (Faceted Gemstone)

Silicon Dioxide (SiO2) with iron impurities

Ironstone Concretion (Moqui Marble variety)

Ferruginous Sandstone Concretion

Agate Geode

Cryptocrystalline Quartz (SiO2)

Quartz

Silicon Dioxide (SiO₂)

Limestone

Sedimentary rock composed primarily of Calcium Carbonate (CaCO3)

Chert nodules in Limestone

Microcrystalline Quartz (SiO2) in Calcium Carbonate (CaCO3) matrix

Undetermined Due to Blur (Possible Flesh-Tone Mineral)

Unknown (Insufficient Visual Clarity)

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Chert (specifically Gray/Tan Chert Node)

Microcrystalline Quartz (SiO2)

Zebra Jasper

Opaque microcrystalline Quartz (SiO2) with impurities

Yellow Quartz Pebble

Silicon Dioxide (SiO2)

Limonite Pseudomorph after Pyrite

Limonite (Hydrous iron oxides, FeO(OH)·nH2O) replacing Pyrite (FeS2)

Banded Agate (Gray/Brown)

Silicon Dioxide (SiO2)

Biotite (Mica)

Biotite group (K(Mg,Fe)3AlSi3O10(F,OH)2)

Gneiss (specifically a Granitic Gneiss)

Gneiss (typically composed of Quartz, Feldspar, and Mica/Amphiboles)

Quartz Pebble

Silicon Dioxide (SiO2)

Jasper (specifically Bloodstone or Heliotrope variety)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Jasper (Imperial Jasper style)

Silicon Dioxide (SiO2) with impurities

Red Jasper

Silicon Dioxide (SiO2) with Iron Oxide (Fe2O3) inclusions

Jasper

Jasper (Silicon Dioxide, SiO2 plus iron oxide impurities)

Milky Quartz Pebble

Quartz (Silicon Dioxide - SiO2)

Clear Quartz

Silicon Dioxide (SiO2)

Chert (Jasper variety)

Silicon Dioxide (SiO2)

Graphic Granite

Pegmatitic Granite (Quartz and Microcline K-Feldspar mixture)

Quartz Pebble (Milky Quartz)

Silicon Dioxide (SiO2)

Limestone with Calcite Veins

Calcium Carbonate (CaCO3)

Limonitic Iron Ore / Goethite

Hydrated Iron(III) oxide-hydroxide (primarily FeO(OH)·nH2O)

Quartzite

Quartzite (Primary mineral: SiO2)

Limestone with Weathering Rind

Calcium Carbonate (CaCO3) - Bioclastic or Micritic Limestone

Bored Siltstone (Holey Rock)

Siltstone with Pholad borings (Lithophaga/Pholadidae trace fossils)

Limestone

Sedimentary Calcite (CaCO3)

Quartz Pebble

Silicon Dioxide (SiO2)

Goethite

Goethite (FeO(OH))

Granite Pebble

Granite (phaneritic igneous rock)

Granodiorite or Diorite

Granodiorite / Diorite

Sandstone

Arenite (primarily SiO2 - Silicon Dioxide)

Chert (Quartz Variety)

Microcrystalline Silica (SiO2)

Red Brecciated Jasper

Silicon Dioxide (SiO2) with Hematite inclusions

Quartz-veined Basalt

Amygdaloidal or Porphyritic Basalt with Silicon Dioxide (SiO2) vein