Mineral (Cryptocrystalline Quartz)

Agate (Polished Cabochon Slice)

Silicon Dioxide (SiO2)

Black Onyx and Mother of Pearl

Cryptocrystalline Quartz (SiO2) and Nacre (Calcium Carbonate)

Jasper

Silicon Dioxide (Microcrystalline Quartz, SiO2)

Tumbled chalcedony (likely carnelian or brown agate)

Microcrystalline quartz, SiO₂; chalcedony with iron-oxide coloration

Botryoidal Chalcedony (Agate)

Silicon Dioxide (SiO2)

Chert (and Flint)

Silicon Dioxide (SiO2)

Chalcedony (likely yellow agate or jasper fragment)

Microcrystalline quartz, SiO₂

Chalcedony (likely agate or chert)

Microcrystalline quartz, SiO₂

Botryoidal chalcedony (gray agate/jasper-like silica)

Microcrystalline quartz, SiO₂; likely chalcedony with opaque quartz or jasper inclusions

Quartz (Chalcedony/Agate nodule)

Silicon dioxide (SiO2)

Banded chert (likely jasper/chert pebble)

Microcrystalline quartz, SiO₂, with iron-oxide and clay/mineral impurities

Geode or Concretion

Silica-based Concretion / Quartz Geode

Banded Agate

Cryptocrystalline Silica (SiO2)

Polished ocean jasper

Orbicular jasper (microcrystalline quartz, SiO₂)

Botryoidal Chalcedony Geode

Silicon Dioxide (SiO2) - Chalcedony / Cryptocrystalline Quartz

Milky Quartz (Water-Worn Pebble)

Quartz (Silicon Dioxide, SiO2)

Banded Agate (with Quartz Geode Center)

Silicon Dioxide (SiO2)

Quartz (Float/Abraded)

Quartz (SiO₂)

Polished agate/jasper slab

Microcrystalline quartz (chalcedony), primarily SiO₂, with iron-oxide inclusions

Chrysoprase-bearing Quartz

Silicon Dioxide with Nickel Inclusions (SiO2)

Carnelian

Carnelian (a variety of Chalcedony, SiO2)

Tumbled brown stone, likely jasper or iron-stained quartz

Microcrystalline quartz (SiO₂), possibly chalcedony/jasper with iron-oxide inclusions

Flint

SiO2 (Microcrystalline Quartz / Chert)

Tumbled banded agate

Microcrystalline quartz (chalcedony), SiO₂, with band-forming impurities

Polished carnelian/chalcedony

Microcrystalline quartz (SiO₂), likely iron-stained chalcedony

Polished agate with black chalcedony inclusion

Banded chalcedony (microcrystalline quartz, SiO₂), likely agate or onyx-type material

Polished brown jasper

Jasper, an opaque microcrystalline variety of quartz (SiO₂), likely iron-rich brecciated or orbicular jasper

Tumbled jasper pebble

Jasper, microcrystalline quartz (SiO₂) with iron-oxide inclusions

Yellow chalcedony (possibly iron-stained agate)

Microcrystalline quartz, SiO₂; yellow coloration likely from hydrated iron oxides

Polished banded agate pebble

Chalcedony (microcrystalline quartz), SiO₂, with iron-oxide or other mineral banding

Agate / Chalcedony Pebble

Silicon Dioxide (SiO2)

Tumbled brown jasper (likely iron-rich chalcedony)

Jasper, opaque microcrystalline quartz (SiO₂), commonly colored by iron oxides

Orbicular jasper (likely ocean jasper)

Silica-rich microcrystalline quartz/chalcedony with iron-oxide and other mineral inclusions; commonly classified as orbicular jasper

Tumbled jasper (likely brecciated or orbicular jasper)

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

Petrified Wood

Silicified Wood (SiO2)

Geode

Quartz nodule / Chalcedony-lined cavity

Petrified Wood

Silicified Wood (Permineralized wood)

Chert

Chert (SiO2)

Polished orbicular jasper (likely ocean jasper)

Jasper, a microcrystalline variety of quartz (SiO₂), with iron-oxide and other mineral inclusions

Tumbled jasper or chert fragment

Microcrystalline quartz (SiO₂), likely jasper/chert with iron-oxide staining

Yellow chalcedony (likely tumbled citrine or yellow jasper)

Microcrystalline quartz, SiO₂; exact variety is uncertain from the image

Polished red jasper

Jasper, opaque microcrystalline quartz (SiO₂) colored mainly by iron oxides