Tektite (Natural Glass)

Rainbow Obsidian

Volcanic glass (SiO2 - approximately 70% or more silicon dioxide)

Tumbled reddish-brown pebble, likely sandstone or iron-rich quartzite

Probable ferruginous sandstone (quartz-rich; SiO₂ with iron oxides), possibly quartzite

Quartz Pebble

Quartz (Silicon Dioxide, SiO2)

Rounded white pebble, likely quartz or feldspar

Most consistent with milky quartz (SiO₂), though altered feldspar or calcite is possible from the image

Amethyst/Smoky Quartz Cluster

Silicon Dioxide (SiO2)

Rounded chert or chalcedony pebble

Microcrystalline quartz (SiO₂), possibly silicified limestone or agate-like chalcedony

Weathered, iron-stained quartzite pebble

Quartzite; predominantly microcrystalline quartz (SiO₂) with iron-oxide staining

Amethyst quartz cluster

Quartz, SiO₂; purple variety colored mainly by iron impurities and irradiation

Chalcedony (possibly agate or common quartz)

Microcrystalline quartz, SiO₂

Yellow Quartz Pebble

Silicon Dioxide (SiO2)

Granite

Granite (composed primarily of Quartz SiO2, Feldspar (KAlSi3O8), and Mica)

Quartz with Mineral Inclusions

Silicon Dioxide (SiO2) with accessory minerals

Red Jasper

Jasper (SiO2) - Silicon Dioxide with Hematic impurities

Red Jasper

Silicon Dioxide (SiO₂)

Red Jasper

Jasper (Silicon Dioxide, SiO2 with Iron Oxide impurities)

Jasper

Silicon Dioxide (SiO2) - Impure Variety of Chert

Jasper

Silicon Dioxide (SiO2) with iron oxide impurities

Jasper (Red Jasper)

Silicon Dioxide (SiO2) with Hematite inclusions

Obsidian flake

Volcanic glass; primarily silica-rich rhyolitic composition (approximately SiO₂)

Yellow Jasper

Silicon Dioxide (SiO2) with Iron Oxide inclusions

Pink Granite

Granite (Phaneritic Felsic Igneous Rock)

Amethyst Geode (Carved)

Amethyst (Violet Crystalline Quartz - SiO2)

Milky quartz (likely quartz vein fragment)

Quartz, silicon dioxide (SiO₂)

Milky quartz

Quartz (silicon dioxide, SiO₂)

Heat-Treated Citrine (Amethyst Cathedral with Agate inclusions)

Silicon Dioxide (SiO2) with iron impurities

Amethyst (purple quartz)

Quartz, silicon dioxide (SiO₂), purple variety colored mainly by iron impurities and irradiation

Polished dark pebble, possibly basalt or chert

Uncertain; likely fine-grained basalt (plagioclase–pyroxene) or microcrystalline silica (chert)

Milky quartz

Quartz (silicon dioxide, SiO₂)

Heat-Treated Amethyst (Commercial Citrine)

Silicon Dioxide (SiO2) - Macro-crystalline Quartz

Amethyst

Silicon Dioxide with trace Iron (SiO2 + Fe3+)

Smoky Quartz

Smoky Quartz (SiO2 - Silicon Dioxide with aluminum impurities)

Amethyst

Silicon Dioxide (SiO2) with iron impurities

Yellow Quartz (Citrine or Quartzite Pebble)

Silicon Dioxide (SiO2)

Tiger's Eye

Pseudomorph of Quartz after Crocidolite (SiO2 with Iron inclusions)

Halite

Sodium Chloride (NaCl)

Herkimer Diamond (Quartz with Carbon Inclusions)

Silicon Dioxide (SiO2) with Anthraxolite inclusions

Blue Quartzite (Aventurine)

Quartzite (primarily SiO2) with inclusions of Dumortierite or Magnesio-riebeckite

Weathered iron-stained quartzite or sandstone cobble

Quartzite (quartz-rich rock), possibly ferruginous sandstone

Polished ocean jasper (orbicular jasper), probable

Microcrystalline quartz (SiO₂), chiefly chalcedony with iron-oxide and other mineral inclusions

Iron-stained chert or siliceous pebble

Microcrystalline quartz (SiO₂), likely ferruginous chert

Tumbled jasper or chalcedony pebble

Microcrystalline quartz, SiO₂ (likely jasper/chalcedony)

Tumbled carnelian/chalcedony

Microcrystalline quartz (SiO₂), likely iron-stained chalcedony