Mineraloid (Human Made Geological Specimen)

Tumbled pink-orange feldspar

Microcline or orthoclase feldspar, KAlSi₃O₈ (tentative)

Tumbled milky quartz

Quartz, silicon dioxide (SiO₂)

Chert Pebble

Microcrystalline Quartz (SiO2)

Banded agate tower (likely onyx/chalcedony)

Microcrystalline quartz, SiO₂; commonly called banded agate or black-and-white onyx

Cut quartz crystal (likely rock crystal)

Quartz, silicon dioxide (SiO₂), trigonal crystal system

Pearl oyster shell with cultured pearls

Mollusk shell (likely Pinctada spp.) containing aragonite pearls, CaCO₃

Tumbled dark stone, likely basalt or slate

Basalt (fine-grained plagioclase–pyroxene rock), possibly slate/phyllite

Tumbled light-colored stone, possibly quartzite or limestone

Indeterminate; likely quartzite (mostly SiO₂) or calcitic limestone (CaCO₃)

Green glass-like cabochon, likely synthetic glass or resin

Unidentified green transparent material; possibly molded glass, synthetic spinel, or resin

Carved stone bowl or mortar

Uncertain; likely steatite (soapstone) or fine-grained volcanic stone

Polished granite egg

Granite, chiefly quartz, feldspar, and dark mica or amphibole

Diamond-set letter “L” jewelry piece

Diamond (crystalline carbon, C) set in a metal mount; the metal is not identifiable from the image

Red coral (likely precious coral)

Corallium sp.; calcium-carbonate skeleton, primarily calcite

Flint (chert)

Microcrystalline quartz, SiO₂

Goldstone beads (likely brown goldstone)

Man-made copper-bearing glass; not a natural mineral. Often sold as “aventurine glass.”

Dyed Pumice

Vesicular Rhyolite (Artificial Coloration Addition)

Blue glassy gemstone-like specimen

Indeterminate; possibly dyed or treated turquoise, blue apatite, or man-made glass

Acrylic or Resin (Synthetic Imitation)

Polymethyl Methacrylate (PMMA) or Polyepoxide

Tumbled milky quartz (likely)

Quartz, silicon dioxide (SiO₂)

Flint (gray chert)

Microcrystalline quartz (SiO₂), a variety of chert

Chert (Flint)

Chert (Microcrystalline Quartz, SiO2)

Obsidian (likely Apache tear or flaked obsidian)

Volcanic glass; primarily rhyolitic silica glass (SiO₂-rich, non-crystalline)

Polished green jasper cabochon (likely serpentine or nephrite imitation)

Jasper: microcrystalline quartz (SiO₂); green coloration may reflect chlorite, epidote, or iron minerals

Man-made Polished Porcelain Tile (Artificial Geologic Lookalike)

Fused Silicate Ceramic with Alumina (Synthetic Kaolinite derivative)

Probable amber fragment

Amber (fossilized plant resin; chiefly amorphous organic resin, commonly dominated by succinite)

Tumbled gray-blue stone, likely quartz-rich feldspar or granite pebble

Probable granitic fragment: quartz (SiO₂) with feldspar and minor mica; exact identification requires testing

Painted River Rock

Anthropogenic-modified Siliciclastic Sedimentary Rock

Tumbled black obsidian (likely)

Volcanic glass; chiefly silica-rich rhyolitic glass (SiO₂)

Polished orbicular/porphyritic granite or breccia

Likely potassium-feldspar–quartz granite with amphibole/biotite and epidote; exact variety uncertain from the image

Muscovite mica

Muscovite, KAl₂(AlSi₃O₁₀)(OH)₂

Tumbled milky quartz

Quartz (silicon dioxide, SiO₂)

Polished black stone, likely shungite

Shungite; carbon-rich mineraloid composed mainly of amorphous carbon, with silica and other minerals

Likely sandstone pebble

Quartz-rich sandstone (composition uncertain from the image)

Quartz geode with druzy crystals

Quartz (SiO₂), likely with iron-oxide staining and darker host rock

Chert (varietal Flint)

Microcrystalline quartz (SiO2)

Pearl

Calcium Carbonate (CaCO3) with Conchiolin

Chert (Jasper variety)

Silicon Dioxide (SiO2)

Pearl

Calcium Carbonate (Aragonite or Calcite) and Conchiolin

Amethyst bead bracelet

Amethyst, purple quartz (SiO₂)

Tumbled blue-gray stone, likely marble or quartzite

Indeterminate; probably calcite marble (CaCO₃) or quartzite (SiO₂)

Chert (specifically Jasper or Flint)

Cryptocrystalline Quartz (SiO2)

Polished fossilized wood (likely petrified wood)

Silicified wood; primarily quartz (SiO₂) replacing wood tissue