Anthropogenic (Man Made Material Mimicking Sedimentary Rock)

Weathered chert or chalcedony nodule

Microcrystalline quartz (SiO₂), possibly silicified limestone or agate-like chalcedony

Polished black stone, likely obsidian

Obsidian (volcanic glass; mostly silica-rich rhyolitic composition)

Slate

Metamorphic Pelitic Rock

Pyrite in Quartz (Drill Core)

Silicon Dioxide (SiO2) with Iron Sulfide (FeS2) inclusions

Tumbled milky quartz pebble

Quartz (silicon dioxide, SiO₂), likely milky quartz

Chert (Flint)

Silicon Dioxide (SiO2)

Blue chalcedony (likely dyed or treated)

Microcrystalline quartz, SiO₂ (chalcedony)

Chert (Flint)

SiO2 (Microcrystalline Quartz)

Flint

Silicon dioxide (SiO2)

Opalite (likely imitation opal glass)

Man-made opalescent glass; not a natural mineral (often sold as opalite)

Weathered concrete or cementitious slab (not natural rock)

Artificial calcium-silicate cement composite; likely Portland cement concrete

Clear quartz sphere

Quartz (silicon dioxide, SiO₂)

Carborundum (Silicon Carbide)

Silicon carbide (SiC)

Sandstone (likely Fossiliferous)

Arenite / Fossiliferous Sandstone (SiO2 composition)

Chert Nodule

Microcrystalline Quartz (SiO2)

Blue Impression Jasper beads

Impression jasper (microcrystalline quartz/chalcedony), chiefly SiO₂, with iron-oxide and other mineral inclusions

Blue opalite glass (likely man-made)

Opalite glass; a silica-based amorphous glass, not natural opal

Man-made Metal Pin (Non-geological)

Antimony-Lead Alloy or Zinc/Brass Base with Electroplating

Polished black stone, likely black obsidian

Obsidian (volcanic glass), chiefly silica-rich rhyolitic composition

Green glass cabochon or tumbled stone

Indeterminate; likely man-made glass, possibly aventurine glass rather than a natural mineral

Flint (chert) nodule

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

Slag

Anthropogenic Vitrophyre (Iron or Smelting Slag)

Tumbled milky quartz pebble

Quartz (silicon dioxide, SiO₂)

Coquina (Fossiliferous Limestone)

Biogenic Limestone (Calcium Carbonate, CaCO3)

Sandstone

Arenite (siliciclastic sedimentary rock composed mostly of quartz)

Obsidian (likely black volcanic glass)

Obsidian; primarily amorphous volcanic silica glass, approximately SiO₂-rich rhyolitic composition

Possible obsidian or slag glass

Volcanic glass, primarily SiO₂; alternatively industrial iron-rich glassy slag

Asphalt (Bituminous Concrete)

Asphaltum / Bitumen-Aggregate Matrix

Chert (Chert / Flint)

Microcrystalline Quartz (SiO2)

Mixed beach-stone and tumbled-glass collection

Predominantly uncertain rocks (likely basalt, granite, and quartz-bearing stones) with anthropogenic glass; one possible banded agate or jasper

Small greenish crystal/mineral fragment

Indeterminate; possibly olivine, quartz, or a green gemstone fragment

Concrete or asphalt-like aggregate surface with a dark fragment

Uncertain; likely artificial concrete containing mixed lithic aggregate, not a natural rock

Painted River Pebble (likely Basalt or Greywacke)

Aphanitic Lithic Clast with Anthropogenic Pigment coating

Chert (and Agate/Chalcedony)

Microcrystalline Quartz (SiO2)

Opalite (likely man-made opalescent glass)

Opalite; not a true mineral, typically synthetic opalescent glass (silica-based)

Possible tektite or iron-rich slag-like natural specimen

Uncertain; possibly natural glass (tektite) or magnetite-rich rock

Slag Glass (Cullet)

Amorphous Silicon Dioxide (SiO2) with metal oxide colorants

Chert Arrowhead

Microcrystalline Quartz (SiO2)

Chalk

Carbonate rock (mainly CaCO3)

Tumbled clear quartz (rock crystal)

Quartz, silicon dioxide (SiO₂)

Sandstone

Arenite

Chert Arrowhead

Microcrystalline Quartz (SiO2)