Tektite (Impact Glass)

Likely obsidian (possibly tektite or slag glass)

Volcanic glass; primarily SiO₂, noncrystalline

Raw green fluorite (probable)

Fluorite, calcium fluoride (CaF₂)

Tumbled milky quartz

Quartz (silicon dioxide, SiO₂)

Libyan Desert Glass

Libyan Desert Glass (SiO2 with trace elements)

Sea Glass (often mistaken for Gemstones)

Amorphous Silica (SiO2) with trace additives

Quartz (River Pebble)

Silicon Dioxide (SiO2)

Chert / Quartz Pebble

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Quartzite Pebble

Metamorphosed Quartz Sandstone (SiO2)

Polymict breccia (likely impact breccia)

Polymict lithic breccia; composition appears basaltic/mafic clasts in a dark, fine-grained matrix

Likely translucent quartz/chalcedony fragment

Silicon dioxide (SiO₂), probably microcrystalline quartz or quartz

Chert (Flint)

Chert (SiO2)

Quartzite River Rock

Quartzite (primarily SiO2)

Purple fluorite cluster

Fluorite (calcium fluoride, CaF₂)

Chert Pebble (Flint)

Microcrystalline/Cryptocrystalline Quartz (SiO2)

Quartz River Pebble

Quartz (Silicon Dioxide, SiO2)

Quartzite River Cobble

Quartzite (primarily SiO2)

Moonstone

Adularia or oligoclase feldspar, commonly showing adularescence

Quartzite River Rock

Metamorphic Quartzite (SiO2)

Obsidian (likely black obsidian)

Volcanic glass; predominantly rhyolitic silica-rich melt (approximately 70–80% SiO₂)

Milky quartz

Quartz (silicon dioxide, SiO₂)

Flint or chert

Microcrystalline quartz (SiO₂), commonly chalcedony with possible impurities

Quartz Pebble (River Agate / Chalcedony)

Silicon Dioxide (SiO2)

Tumbled blue chalcedony

Chalcedony, microcrystalline quartz (SiO₂)

Pyrite (Fool's Gold)

Iron Pyrite (FeS2)

Quartz Pebble

Silicon Dioxide (SiO2)

Libyan Desert Glass

Natural Silica Glass (SiO2 with minor iron and titanium)

Rounded river or beach pebble

Likely quartz-rich sandstone or quartzite; exact identification requires a close-grained view and hardness test

Tumbled quartz crystal

Quartz (silicon dioxide, SiO₂)

Polished snowflake obsidian

Obsidian, volcanic glass (SiO₂-rich rhyolitic composition) with cristobalite spherulites

Cut gemstone, likely diamond

Diamond (crystalline carbon, C)

Quartz Pebble

Silicon Dioxide (SiO2)

Labradorite cabochon

Labradorite, a calcium-rich plagioclase feldspar; approximately (Ca,Na)(Al,Si)₄O₈

Quartz (River Cobble)

Silicon Dioxide (SiO2)

Red cabochon gemstone, likely carnelian or dyed chalcedony

Chalcedony (microcrystalline quartz), SiO₂; exact identification requires testing

Quartz Pebble (Beach Agate / Chalcedony Pebble)

Silicon Dioxide (SiO2)

Polished mahogany obsidian

Volcanic glass; predominantly silica-rich rhyolitic composition (SiO₂)

Quartz Pebble

Silicon Dioxide (SiO2)

Rounded river pebble

Indeterminate lithic clast; likely weathered sandstone or quartz-rich sedimentary rock

Smoky Quartz with Iron Inclusions

Silicon Dioxide (SiO2)

Quartz (Sea Glass or River-worn Pebble style)

Silicon Dioxide (SiO2)

Quartz Pebble (Sea Glass-like texture)

Silicon Dioxide (SiO2)

Pumice

Vesicular Rhyolite / Pumice