Glass

Tumbled milky quartz

Quartz, silicon dioxide (SiO₂)

Pink quartz (likely rose quartz)

Rose quartz; quartz, SiO₂

Amethyst geode

Quartz (SiO₂), purple variety amethyst; commonly in basalt-hosted geodes

Tumbled amethyst

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

Slag (Industrial Byproduct)

Ferro-silicate glass (Slag)

Milky quartz-rich rock

Quartz, silicon dioxide (SiO₂), possibly quartzite or a quartz-bearing pegmatite fragment

Slag Glass (Cullet)

Amorphous Silica / Glass residue

Quartz (Citrine or Iron-Stained)

Silicon Dioxide (SiO2)

Quartz-rich rock, likely milky quartz or quartz vein fragment

Quartz (silicon dioxide, SiO₂), possibly with minor feldspar or calcite

Tumbled quartz-rich stone, possibly milky quartz or quartzite

Quartz (SiO₂), potentially quartzite if metamorphic

Rose Quartz

Silicon dioxide (SiO2) with trace amounts of titanium, iron, or manganese

Possible tektite (natural impact glass)

Impact glass; composition and origin cannot be confirmed from the image

Opalite

Synthesized glass / Silicon dioxide

Zeolite in Host Rock

Hydrated aluminosilicate mineral group

Pumice

Pumice

Tumbled milky quartz, possibly quartzite

Quartz (SiO₂); the specimen may be a quartz-rich metamorphic rock if its texture is granular

Greenish quartz (likely prase/chalcedony)

Quartz, SiO₂; possibly green chalcedony or chlorite-included quartz

White quartz pebble

Quartz (SiO₂), likely milky quartz

Milky quartz pebble

Quartz (silicon dioxide, SiO₂)

Rounded metamorphic pebble, likely quartzite or weathered gneiss

Quartzite (mostly quartz, SiO₂) or micaceous gneiss; exact identification requires testing

Tumbled white quartz pebble

Quartz (silicon dioxide, SiO₂), likely milky quartz or chalcedony

Quartz Vein / Quartz Matrix

Silicon Dioxide (SiO2)

Chert (Flint)

Cryptocrystalline Quartz (SiO2)

Quartz (Milky Quartz)

Silicon Dioxide (SiO2)

Chert (Flint)

Cryptocrystalline Quartz (SiO2)

Citrine Quartz

Silicon Dioxide (SiO2) with iron impurities

Chert (Chalcedony/Flint)

Silicon Dioxide (SiO2)

Pink quartz (likely rose quartz)

Quartz, silicon dioxide (SiO₂)

Chert (Flint)

Microcrystalline Quartz (SiO2)

Chert (Arrowhead Preform)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

River Pebble (likely Quartzite or Quartz)

Quartzite (SiO2)

Chert (with Limestone and Iron Oxide staining)

Cryptocrystalline Quartz (SiO2)

Chert (Iron-stained)

Microcrystalline Quartz (SiO2)

Chert / Flint

Chert (Microcrystalline Quartz, SiO2)

Faceted yellow-brown gemstone earring

Likely citrine (quartz, SiO₂), though treated quartz or synthetic glass cannot be confirmed from the image

Milky Quartz

Silicon Dioxide (SiO2)

Yellow Quartz (Citrinated Quartz)

Silicon Dioxide (SiO2)

Banded chert (likely flint or jasperoid)

Microcrystalline quartz/chalcedony, SiO₂

Tumbled reddish-brown stone, likely iron-stained sandstone or quartzite

Probable ferruginous sandstone; exact identification requires testing

Likely smoky quartz or quartz-rich tumbled fragment

Quartz, silicon dioxide (SiO₂), possibly smoky quartz

White quartz-rich pebble, possibly chalcedony or milky quartz

Quartz (SiO₂), potentially microcrystalline quartz (chalcedony)

Small brown quartz-rich pebble, possibly chert or jasper

Microcrystalline quartz (SiO₂), tentative