Sedimentary (Secondary Classification: Cryptocrystalline Quartz)

Jasper pebble

Silicon dioxide (SiO2) with iron oxide inclusions

Sandstone

Arenite (Secondary classification based on grain size)

Sandstone Cobble

Arenite (Secondary classification based on grain size)

Polished yellow-brown jasper

Jasper, a microcrystalline variety of quartz (SiO₂), commonly containing iron-oxide impurities

Small weathered mineral/rock fragment

Indeterminate; possibly quartz-bearing feldspathic rock or calcite-rich specimen

Quartz-rich chalcedony (likely silicified rock)

Microcrystalline quartz, SiO₂; possibly silicified limestone or jasper

Polished brecciated jasper

Jasper, an opaque microcrystalline quartz variety; primarily SiO₂ with iron-oxide and clay inclusions

Petrified wood

Silicified wood; commonly quartz/chalcedony (SiO₂) replacing organic tissue

Milky quartz-bearing rock, possibly quartzite

Quartz (SiO₂), likely in a quartzite or quartz-rich vein

Weathered quartz-rich rock, possibly chert or quartzite

Likely microcrystalline quartz (SiO₂), but exact identification is uncertain from the photograph

Chalcedony

Cryptocrystalline Quartz (SiO2)

Jasper

SiO2 (Cryptocrystalline quartz)

Quartz-rich rock fragment, possibly chert or weathered quartz

Microcrystalline quartz (SiO₂), tentative identification

Weathered gray-green basaltic rock

Basalt, likely altered to low-grade greenschist/amphibolite facies

Druzy Chalcedony (Agate Geode)

Silica (SiO2) - Cryptocrystalline Quartz with druzy macrocrystalline quartz

Chalcedony (Agate/Carnelian pebbles)

Cryptocrystalline Quartz (SiO2)

Quartz-bearing dark rock, possibly hornfels or basalt

Probable quartz–feldspar rock; exact identification requires testing

Coarse-grained metamorphic rock, likely gneiss

Biotite–quartz–feldspar gneiss (probable; exact identification requires a fresh surface and tests)

Agate Pebble / Quartz Pebble

Cryptocrystalline Quartz (SiO2)

Chert with Quartz Veining

Microcrystalline Silica (SiO2)

Granite (likely biotite granite)

Coarse-grained granitic rock; chiefly quartz, potassium feldspar, plagioclase, and biotite/hornblende

Chert (River Pebble)

Cryptocrystalline Quartz (SiO2)

Chert (with Quartz Veining)

Microcrystalline Quartz (SiO2)

Polished kambaba jasper

Orbicular stromatolitic jasper; microcrystalline quartz (SiO₂) with chlorite/amphibole-rich inclusions

Conglomeratic breccia

Clast-supported polymictic conglomerate/breccia, cemented by silica- or carbonate-rich matrix

Banded Agate

Cryptocrystalline Quartz (SiO2)

Polished leopard jasper (orbicular or brecciated jasper)

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

Chalcedony (Agate) Pebble

Silicon Dioxide (SiO2)

Agate

Cryptocrystalline Quartz (SiO2)

Chert (Jasper/Agate variety)

Cryptocrystalline Quartz (SiO2)

Weathered quartz-rich rock, possibly quartzite or granite fragment

Quartzite (SiO₂-dominant) or altered granitoid; uncertain from image

Breciated Chert

Brecciated Chert (Microcrystalline Quartz, SiO2)

Jasper

Cryptocrystalline Quartz (SiO2)

Jasper (specifically Bloodstone/Heliotrope or Dark Green Jasper)

Cryptocrystalline Quartz (SiO2) with inclusions

Likely mica-rich granite pegmatite

Granitic pegmatite, composed mainly of quartz and feldspar with visible mica (likely muscovite or biotite)

Chalcedony in Limestone Host Rock

Silicon Dioxide (SiO2) within Calcium Carbonate (CaCO3)

Quartz-rich granitic rock (likely granite or granitic pegmatite)

Granite/pegmatite; chiefly quartz (SiO₂), feldspar, and mica

Agate

Cryptocrystalline Silicon Dioxide (SiO2)

Red jasper pebble

Microcrystalline quartz (chalcedony), SiO₂, colored by iron oxides

Flint Nodule

Chert (Cryptocrystalline Quartz, SiO2)

Weathered iron-rich rock, possibly banded iron formation

Hematite–goethite-rich ironstone; possible BIF (Fe₂O₃/FeO(OH) with quartz)

Quartz (Chert/Chalcedony variety)

Silicon Dioxide (SiO2)