Mineraloid (Human Made Geological Specimen)

Goldstone

Avventurina (Cu + SiO2 glass)

Quartz (Pebble)

Quartz (SiO₂)

Green Glass Cullet / Recycled Glass

Amorphous Silicon Dioxide (SiO2) with various metal oxides

Polished dark river pebble

Likely fine-grained basalt or chert; exact identification requires testing

Sandstone Concretion

Sedimentary Concretion (Quartz sandstone with iron oxide cement)

Chalk

Micrite (primarily Calcium Carbonate, CaCO3)

Polished brown river pebble, likely quartzite

Quartzite (mostly microcrystalline SiO₂), identification tentative from appearance

Chert (or Flint)

Microcrystalline quartz (SiO2)

Iron-rich sandstone or lateritic rock

Ferruginous sandstone; predominantly quartz (SiO₂) cemented or stained by iron oxides/hydroxides

Obsidian

Volcanic glass (SiO2 - Silicon Dioxide with impurities)

Sandstone (Red/Brown Variety)

Arenite (composed primarily of SiO2 with Fe2O3 iron oxide inclusions)

Milky quartz (likely tumbled or polished)

Quartz, silicon dioxide (SiO₂)

Amber

Succinite (a specific common type) or Fossilized Tree Resin (C10H16O)

Polished brown agate or jasper

Microcrystalline quartz, SiO₂ (chalcedony variety; exact identification uncertain)

Painted Rock / Geode Specimen

Silicon Dioxide with artificial pigment coating

Blue obsidian-like volcanic glass

Volcanic glass, chiefly silica-rich amorphous material (composition uncertain)

Banded calcite tower (often sold as “onyx” or honey calcite)

Calcite, CaCO₃

Iron-stained chert (flint) nodule

Microcrystalline quartz (SiO₂), with iron-oxide staining

Chert Pebble

Chert (Microcrystalline Quartz, SiO2)

Pink calcite (likely)

Calcite — calcium carbonate, CaCO₃

Crackle Agate / Dyed Quartz

SiO2 (Silicon Dioxide)

Quartz (Microcrystalline/Chert)

Silicon Dioxide (SiO2)

Limonite (Iron Ore)

Limonite (Hydrated iron oxide - FeO(OH)·nH2O)

Rounded gray-brown pebble

Indeterminate; likely weathered quartz-rich sandstone or fine-grained volcanic rock

Obsidian

Volcanic glass

Milky quartz (likely quartz fragment)

Quartz, silicon dioxide (SiO₂)

Tumbled chalcedony (likely carnelian/agate)

Microcrystalline quartz, SiO₂; chalcedony, with possible iron-oxide coloring

Chert (Jasper variety)

Microcrystalline Quartz (SiO2)

Agate

Silicon Dioxide (SiO2) - Cryptocrystalline Chalcedony

Polished dendritic agate or jasper

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

Tumbled carnelian/chalcedony

Microcrystalline quartz (SiO₂), iron-oxide-stained chalcedony

Tumbled quartz-rich stone, possibly milky quartz or quartzite

Quartz (SiO₂), potentially quartzite if metamorphic

Snowflake Obsidian

Spherulitic Volcanic Glass (SiO2 + impurities)

Clear quartz crystal

Quartz (silicon dioxide, SiO₂)

Mixed gravelly conglomeratic road aggregate

Polymictic clast-supported conglomerate or fill; composition varies, commonly quartz, feldspar, basalt, and weathered rock fragments

Red Painted Rock

Artificial Coated Lithic Fragment

Chert (Common Variety, Jasper)

Microcrystalline Quartz (SiO2)

Petrified Wood

Silicified Wood (SiO2)

Tumbled polymictic stone, likely jasper-bearing conglomerate

Siliciclastic conglomerate with microcrystalline quartz (jasper/chert) and altered volcanic or feldspathic clasts

Yellow calcite cabochon

Calcite (calcium carbonate, CaCO₃), likely honey/yellow calcite

Tumbled pale-green stone, likely prehnite or serpentine

Most consistent with massive prehnite, Ca₂Al₂Si₃O₁₀(OH)₂; serpentine is a possible alternative

Amber

Succinite (fossilized resin); C10H16O