Multiple

Quartzite Cobble

Quartzite (SiO2)

Diamond (Cluster Setting)

Carbon (C) - Diamond

Unakite

Epidotized Granite

Sphalerite with Galena

Zinc Sulfide ((Zn,Fe)S) and Lead Sulfide (PbS)

Quartzite (River Cobble)

Quartzite (Metamorphosed Quartz Sandstone, SiO2)

Chert / River Pebble

Microcrystalline Silica (SiO2)

Lapis Lazuli

Lazurite (primary mineral component), (Na,Ca)8(AlSiO4)6(S,SO4,Cl)1-2

Quartzite Pebble

Quartzite (SiO2)

Quartzite Cobble

Metamorphosed Quartz Sandstone (primarily SiO2)

Ventifact

Eolian Ventifact (often composed of basalt, chert, or quartzite)

Quartzite Pebble

Quartzite (primarily SiO2)

Fossiliferous Limestone with Crinoid Stem Impression

Calcium Carbonate (CaCO3) matrix with Crinoidea fossil

Knightia Fossil in Limestone

Knightia eocaena in micritic limestone

Milky Quartz Pebble

Quartz (Silicon Dioxide, SiO2)

Desert Rose (Baryte/Gypsum Rosette)

Baryte (BaSO4) or Gypsum (CaSO4·2H2O)

Chert / Jasper

Sedimentary Cryptocrystalline Quartz (SiO2)

Unakite

Epidotized Granite

Yellow Quartzite (Onyx Pebble)

Silicon Dioxide (SiO2) - Quartzite

Riverstone Quartzite (Water-worn Siltstone/Quartzite)

Metamorphosed Quartz-rich Arenite (SiO2)

Satin Spar (Gypsum)

Hydrous Calcium Sulfate (CaSO4·2H2O)

Greywacke with Quartz Veins

Lithic Sandstone (Greywacke) with SiO2 inclusions

Agate

Silicon Dioxide (SiO2) - variety of Chalcedony

Chert (Hag Stone / Hole Stone)

Chert (Cryptocrystalline variety of Quartz, SiO2)

Fossilized Turritella Gastropod (Internal Mold)

Turritella (Fossil Gastropod Crust)

Crinoid Stem Fossil

Class Crinoidea (Phylum Echinodermata), primarily Calcium Carbonate (CaCO3)

Fire Agate

SiO2 (Silicon Dioxide with Iron Oxide inclusions)

Red Jasper

Silicon Dioxide (SiO2) with Hematite inclusions

Yellow Quartzite River Cobble

Meta-quartzite (SiO2 with iron oxide staining)

Lapis Lazuli (Lazurite crystals on Marble)

Lazurite / (Na,Ca)8[(S,Cl,SO4,OH)2|(AlSiO4)6]

Herkimer Diamond in Matrix

Quartz (SiO2) in Dolostone (CaMg(CO3)2)

Arid Sandy Loam

Arenosols / Regosols

Agate Geode Node

Cryptocrystalline Quartz (SiO2)

Botryoidal Chalcedony

Cryptocrystalline Silicon Dioxide (SiO2)

Mother of Pearl (Nacre)

Calcium Carbonate (primarily aragonite, with conchiolin)

Rhodonite, Gray Moonstone, and White Feldspar Mix

Multiple: MnSiO3 (Rhodonite), (K,Na)AlSi3O8 (Feldspar/Moonstone)

Mixed Tumbled Gemstones (Agate, Aventurine, Pyrite, etc.)

Multiple (principally Silicon Dioxide SiO2 and Iron Disulfide FeS2)

Carved Mottled Greenish-Yellow Crystal/Glass Object

Unknown; possibly a form of quartz (chalcedony/jadeite/nephrite) or glass/resin.

Clear Quartz (or Rock Crystal)

Quartz (SiO₂ - Silicon Dioxide)

Fluorite

Fluorite (Calcium Fluoride, CaF2)

Botryoidal Hematite (Kidney Ore)

Hematite (Fe2O3)

Fluorite

Fluorite (Calcium Fluoride - CaF2)

Quartz (likely) or a Quartzite Pebble

Silicon dioxide (SiO2) for quartz. If it's quartzite, it's a metamorphic rock primarily composed of quartz.