Metamorphic Or Igneous (Context Dependent)

Polished banded agate (likely purple chalcedony/jasper)

Microcrystalline quartz, SiO₂; chalcedony with iron-oxide-rich jasper bands

Limestone

Calcium Carbonate (CaCO3)

Graywacke

Graywacke

Milky quartz vein fragment

Quartz (silicon dioxide, SiO₂), massive/microcrystalline variety

Ferruginous Sandstone (Ironstone Conglomerate fragments)

Ferruginous clastic sedimentary rock (SiO2 cemented by Fe2O3)

Sandstone Concretion

Limonitic Sandstone Concretion

Limonite-pseudomorph after Pyrite (Prophecy Stone)

Goethite and Limonite secondary minerals (FeO(OH)·nH2O) replacing Pyrite (FeS2)

Yellow Jasper

Chalcedony (SiO2) with iron oxide inclusions

Ironstone Concretion (Moqui Marble)

Iron-oxide concretion (Fe2O3 / FeO(OH))

Mica (Biotite or Phlogopite variety)

Phyllosilicate (complex mineral formula involving K, Mg, Fe, Al, Si, and O)

Milky quartz vein rock

Quartz (SiO₂), likely in a quartz-rich host rock with minor iron-stained minerals

Bull Quartz (Milky Quartz)

Silicon Dioxide (SiO2)

Weathered orange-brown stone, possibly iron-stained sandstone

Unconfirmed; likely quartz-rich sandstone with iron-oxide staining

Coprolite

Fossilized Feces

Orange glassy slag (industrial by-product)

Iron-rich silicate glass; composition varies, commonly Fe–Ca–Al silicate

Blue Sapphire

Corundum (Al2O3) with traces of Iron and Titanium

White quartz-rich pebble

Likely quartzite or milky-quartz pebble (SiO₂)

Gold-bearing quartz vein rock

Milky quartz (SiO₂) with probable native gold and iron-oxide staining

Blue cabochon gemstone ring

Uncertain; likely blue sapphire (corundum, Al₂O₃), blue topaz, or synthetic glass/spinel

Fossilized shell fragment

Likely a fossil mollusk shell; exact taxon cannot be determined from the image

Likely brown chert (flint)

Microcrystalline quartz (SiO₂), variety chert/flint

Tumbled amethyst

Amethyst, purple quartz (SiO₂)

Jasper Marble

Silicon Dioxide (SiO2) with Impurities

Red faceted gemstone ring

Likely synthetic ruby or red spinel; exact identification requires testing

Quartz Vein in Host Rock

Silicon Dioxide (SiO2) within Metasedimentary or Igneous Matrix

Tiger's Eye (often misinterpreted as Gold Ore in this context)

Pseudomorph of Quartz after Crocidolite (SiO2)

Massive Quartz with Host Rock

Silicon Dioxide (SiO2)

Yellow faceted gemstone, likely citrine or yellow sapphire

Uncertain; probable quartz (SiO₂) or corundum (Al₂O₃)

Chert (varietal Chalcedony or Flint)

Silicon dioxide (SiO2) - Microcrystalline Quartz

Polished orbicular jasper

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

Red Sandstone

Arenite (Ferruginous Sandstone)

Likely milky quartz fragment

Quartz (silicon dioxide, SiO₂)

Rounded sandstone pebble

Clastic sandstone, chiefly quartz and feldspar grains cemented by iron oxides and silica

Chert (Flint Nodules)

Silicon Dioxide (SiO2)

Chert (with nodule)

Microcrystalline Quartz (SiO2)

Banded chert or jasper pebble

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

Tumbled amethyst (likely)

Quartz, SiO₂; purple coloration from trace iron and irradiation

Flint/chert projectile point

Microcrystalline quartz (SiO₂), archaeologically worked into a bifacial point

Chert (Cream Variety)

Microcrystalline silica (SiO2)

Red Sandstone

Arenite (primarily SiO2 with Fe2O3)

Milky quartz (iron-stained quartz)

Quartz, silicon dioxide (SiO₂)

Rose quartz

Quartz (SiO₂), pink variety