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

Amethyst Geode

Silicon Dioxide (SiO2) with iron impurities

Quartz Pebble

Quartz (Silicon Dioxide, SiO2)

Chert (Jasper/Quartzite river stone)

Microcrystalline Silicon Dioxide (SiO2)

Chert (often called Flint in this context)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Druzy Quartz Geode (Oco or Moroccan variety)

Silicon Dioxide (SiO2)

Rainbow Hematite (Titanium Coated)

Iron(III) oxide (Fe2O3) with Titanium/Metal Oxide coating

Quartz (Druzy/Macro-crystalline)

Silicon Dioxide (SiO2)

Tiger's Eye (Mineral Collection)

Tiger's Eye (SiO2 with crocidolite inclusions)

Granite Pebble (River Rock)

Granite (composed primarily of Quartz, Feldspar, and Mica)

Snowflake Obsidian

Volcanic glass with Spherulite inclusions (SiO2)

Amethyst Cluster

Amethyst (Silicon Dioxide), chemical formula: SiO2

Chalcedony (Agate/Blue Quartzite)

Silicon Dioxide (SiO2)

Basalt

Basalt (principally Plagioclase and Pyroxene)

Limestone Fragment

Sedimentary rock (primarily Calcium Carbonate, CaCO3)

Chert (often called Flint when dark or worked)

Cryptocrystalline silica (SiO2)

Amethyst (Quartz variety)

Amethyst [Silicon Dioxide (SiO2)]

Carnelian

Carnelian (SiO2, Silicon Dioxide with Iron Oxide impurities)

Mookaite Jasper

Silicified Radiolarite (SiO2)

Sandstone (likely Graywacke or Lithic Sandstone)

Arenite / Wacke (SiO2 based with lithic fragments)

Cinnabar in Quartz

Silicon Dioxide (Quartz, SiO2) with Mercury Sulfide inclusions (Cinnabar, HgS)

Aragonite / Calcite Geode

Calcium Carbonate (CaCO3)

Quartz (Milky/Sugar variety)

Silicon Dioxide (SiO2)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Petrified Wood

Silicified Wood (primarily SiO2)

Chert Pebble

Microcrystalline Quartz (SiO2)

Banded Gneiss

Gneiss (High-grade Regional Metamorphic Rock)

Bivalve Fossil (Shell Fragment)

Class Bivalvia (Calcium Carbonate - CaCO3)

Blue Lace Agate (Variety of Chalcedony)

Silicon Dioxide (SiO2)

Chert

Chert (Silicon Dioxide, SiO2)

Amethyst Geode

Silicon Dioxide (SiO2) with trace Iron (Fe3+) impurities

Chert (Polished River Pebble)

Chert (SiO2)

Petrified Wood

Silicified Wood (primarily Quartz / Chalcedony: SiO2)

Green Quartz (Prasiolite variant or Aventurine)

Silicon Dioxide (SiO2)

Milky Quartz with Iron Staining

Quartz (Silicon Dioxide, SiO2)

Arkosic Sandstone (or Conglomeritic Sandstone fragment)

Arkose (rich in feldspar)

Ruby (set in a gold pendant)

Ruby (Variety of Corundum, Al2O3)

Amethyst and Citrine (Quartz variants)

Silicon Dioxide (SiO2)

Diamond Druzy (Crystalline Diamond)

Carbon (C)

Geode (Unopened)

Silica-rich concretion (SiO2)

Tree Agate

Dendritic Agate (Silicon Dioxide, SiO2)

Citrine Geode Fragment

Citrine (Silicon Dioxide with Iron Impurities), SiO2

Banded Chert (Flint)

Microcrystalline Quartz (SiO2)