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

Quartzite Cobble

Quartzite (composed primarily of SiO2)

Marble (Sculculpted)

Metamorphosed Limestone (primarily CaCO3)

Tree Agate

Silicon Dioxide (SiO2) with dendritic inclusions

Calcite

Calcite (Mineral; CaCO₃)

Quartz

Silicon Dioxide (SiO2)

Sandstone (with Iron Staining)

Clastic sedimentary rock (primarily Quartz with Limonite/Goethite staining)

Sandstone

Clastic sedimentary rock (primarily SiO2)

Sandstone

Arenite (predominantly SiO2)

Sand Dollar Fossil

Echinoidea (Clypeasteroida)

Black River Stone (likely Basalt or Chert)

Basalt (primarily Plagioclase Feldspar and Pyroxene)

Ferruginous Quartz

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

Apatite

Apatite group mineral (e.g., Fluorapatite - Ca5(PO4)3F, Chlorapatite - Ca5(PO4)3Cl, Hydroxylapatite - Ca5(PO4)3(OH))

Quartz Druzy Geode

Silicon Dioxide (SiO2) - Crystalline Variety

Tree Agate (Dendritic Agate/Quartz)

Silicon Dioxide (SiO2) with trace Manganese or Iron oxide inclusions

Lapis Lazuli

Na6Ca2(Al6Si6O24)(SO4,S,Cl,OH)2 (Lazurite-dominated rock)

Chert (Flint)

Chert (Microcrystalline Quartz, SiO2)

Yellow Calcite

Calcium Carbonate (CaCO3)

Quartz Vein / Milky Quartz

Silicon Dioxide (SiO2)

Massive Cryptocrystalline Quartz (Chert/Chalcedony Pebble)

Silicon Dioxide (SiO2)

Chert (or Flint)

Chert (a cryptocrystalline variety of quartz, SiO2)

Yellow Quartz (Citrine Quartz variety / Ferruginous Quartz)

Silicon Dioxide (SiO2) with iron inclusions

Quartzite Pebble

Quartzite (predominantly Silicon Dioxide - SiO2)

Chert (Flint)

Chert (Silicon Dioxide, SiO2)

Chalcopyrite

Chalcopyrite (CuFeS2)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Clear Quartz Crystal Cluster

Silicon Dioxide (SiO2)

Dendritic Agate

Silicon Dioxide (SiO2) with Manganese/Iron oxide inclusions

Pink Lepidolite

Lepidolite (K(Li,Al)3(Al,Si,Rb)4O10(F,OH)2)

Lapis Lazuli

Lapis Lazuli (Complex silicate mixture containing Lazurite: (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2)

Gneissic River Pebble

Gneiss

Banded Calcite (often marketed as Mexican Onyx or Onyx Marble)

Calcite (Calcium Carbonate, CaCO3)

Chert (Nodule)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert (Jasper variation)

Microcrystalline Quartz (SiO2)

Agate Geode / Nodular Chalcedony

Silicon Dioxide (SiO2) with impurities

Pyrite in Quartz (Drill Core)

Silicon Dioxide (SiO2) with Iron Sulfide (FeS2) inclusions

Feldspar (specifically Orthoclase or Plagioclase)

Potassium Aluminum Silicate (KAlSi3O8) or Sodium/Calcium Aluminum Silicate

River Cobble (Salt and Pepper Gneiss)

Gneiss (High-grade regional metamorphic rock)

Chert Nodule (Flint)

Chert (Silicon Dioxide, SiO2)

Sandstone (clastic)

Clastic Sedimentary Rock (primarily composed of SiO2)

Greywacke (River Pebble)

Greywacke sandstone with quartz veining

Quartzite Pebble

Quartzite (principally SiO2)

Yellow Quartz (Chalcedony/Citrine Pebble)

Silicon Dioxide (SiO2)