Antropogenic (Man Made Material)

Chert (Black Flint)

Silicon Dioxide (SiO2)

Red Sandstone

Arenite (Iron-rich)

Nephrite Jade

Ca2(Mg,Fe)5Si8O22(OH)2

Mother of Pearl (Nacre) / Shell Fragment

Biogenic Calcium Carbonate (Aragonite and Conchiolin)

Chert (Yellow Jasper/Flint)

Microcrystalline Quartz (SiO2)

Chert (and/or Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert (variations include Flint/Jasper)

Cryptocrystalline Quartz (SiO2)

Chert / Jasper

Silicon Dioxide (SiO₂)

Chert (Flint)

Microcrystalline Quartz (SiO2)

Fossilized coral with attached shell

Likely fossil coral (Scleractinia or Tabulata), with a bivalve or gastropod shell; exact identification requires microscopy

Sandstone

Arenite (SiO2 primarily)

Chert (Flint)

SiO2 (Microcrystalline Quartz)

Coquina

Biogenic Limestone (Calcite, CaCO3)

Beaded blue-and-green gemstone jewelry

Likely dyed or treated chalcedony/agate and green aventurine or glass-like stone; exact identification requires testing

Faceted gemstone in a jewelry setting

Indeterminate from image; likely quartz, cubic zirconia, or another transparent faceted stone

Diamond

Carbon (C)

Sandstone (Quartz Arenite)

Sandstone (dominated by SiO2 quartz grains)

Unakite

Altered Granite (Epidotized Granite)

Nacre (Mother of Pearl)

Nacre (Biogenic Aragonite/Calcite composite, CaCO3)

Likely smoky quartz pendant

Smoky quartz, silicon dioxide (SiO₂), quartz variety colored by irradiation-related defects

Likely iron-rich rock or weathered metallic mineral fragment

Uncertain; possibly limonite/goethite or iron-bearing slag

Tumbled brown chalcedony or agate

Microcrystalline quartz (SiO₂), likely chalcedony; possibly iron-stained jasper or agate

Botryoidal chalcedony with iron-oxide staining

Microcrystalline quartz (SiO₂), likely iron-oxide-bearing chalcedony

Diamond

Carbon (C)

Tumbled chalcedony (likely milky quartz)

Microcrystalline quartz, SiO₂; possibly pale agate or quartzite

Red glass-like crystal, likely synthetic ruby or red glass

Uncertain from image; possible corundum (ruby), Al₂O₃, or synthetic glass

Chert (often called Flint)

Chert (Cryptocrystalline Quartz, SiO2)

Fossilized gastropod (likely nerite or related sea snail)

Gastropoda; shell composed originally of aragonite/calcite, commonly replaced or infilled by calcite

Amethyst gemstone ring

Quartz, purple variety — SiO₂

Chert Arrowhead (Lithic Tool)

Microcrystalline quartz (SiO2) - Archeological lithic artifact

Diorite (Gneissic)

Diorite

Tumbled chalcedony or quartz pebble

Microcrystalline quartz (SiO₂), likely orange chalcedony/carnelian

Flint (chert) nodule

Microcrystalline quartz (SiO₂), occurring as a flint/chert nodule in limestone

Beach Pebble (Chalcedony / Chert)

Silicon Dioxide (SiO2)

Green glassy slag (often sold as “sea glass” or “green obsidian”)

Industrial vitreous slag; primarily amorphous silicate glass, composition variable

Sandstone (Quartzose)

Arenite (primarily SiO2)

Quartzite

Metamorphic Quartzite (SiO2)

Granodiorite

Granodiorite

Sandstone

Arenite (variable SiO2 composition)

Flint (chert), likely a worked stone flake

Microcrystalline quartz (SiO₂); cryptocrystalline variety of quartz

Polished orbicular granite heart

Granite, commonly quartz–alkali feldspar–plagioclase–biotite granite; exact locality-dependent

Chert (Flint/Chalcedony)

Silicon Dioxide (SiO2)