Mineralogical Glass

Tektite (Indochinite)

Tektite (High-silica natural glass)

Polished purple chalcedony (likely lavender agate)

Microcrystalline quartz, SiO₂; chalcedony variety, possibly naturally iron- or manganese-colored

Sand Grain (Quartz)

Silicon Dioxide (SiO2)

Quartzite

Quartzite (primarily SiO2)

Snowflake Obsidian

Volcanic Glass with Cristobalite inclusions

Tumbled orange chalcedony and a gray stone disk

Chalcedony (microcrystalline quartz, SiO₂); disk likely fine-grained sandstone or slate

Quartz-rich breccia or vein quartz with iron staining

Microcrystalline to crystalline SiO₂, likely quartz with iron oxides/hydroxides and altered host rock

Blue glass-like tumbled specimen

Most likely cobalt-blue slag glass or manufactured glass; not confidently identifiable as a natural mineral from the image

Citrine

Silicon Dioxide (SiO2)

Manganese Dendrite on Siltstone

Manganese Oxide (pyrolusite or psilomelane) Dendrites

Pyrite Sun (Pyrite Dollar)

Iron Disulfide (FeS2)

Small rounded stone or mineral fragment

Indeterminate; likely a common quartz- or feldspar-bearing silicate fragment

Sandstone

Clastic sedimentary rock (primarily SiO2)

Tumbled gray chalcedony or quartz pebble

Microcrystalline quartz (SiO₂), possibly gray chalcedony

Quartz Pebble

Silicon Dioxide (SiO2)

Brown chert or flint pebble

Microcrystalline quartz (SiO₂), commonly with chalcedony and iron-oxide staining

Geode with Quartz/Chalcedony

Silicon Dioxide (SiO2)

Flint or chert flake

Microcrystalline quartz (SiO₂), commonly chert/flint

Chert or flint nodule

Microcrystalline quartz (SiO₂), commonly chalcedony with possible opaline silica

Reddish-brown crystalline rock, possibly weathered granite or garnet-bearing schist

Indeterminate; likely quartz–feldspar–mica rock with iron oxides, potentially garnet-bearing

Tumbled chert or flint pebble

Microcrystalline quartz (SiO₂), likely chert

Polished greenstone pebble (likely epidote-bearing stone)

Epidote–chlorite amphibolite or altered basalt; composition likely epidote, chlorite, amphibole/pyroxene, and iron oxides

Quartzite

Metamorphosed Quartz Sandstone (SiO2)

Graphite-bearing quartz-mica schist

Graphite-rich quartz–mica schist; primarily quartz (SiO₂), muscovite/biotite, and graphite (C)

Quartzite

Quartzite (SiO2)

Dalmatian jasper (likely orbicular microgranite)

Quartz–feldspar–biotite/pyroxene microgranite; commonly marketed as Dalmatian jasper

Dendritic Quartz

Silicon Dioxide (SiO2) with Manganese Oxide inclusions

Tumbled green aventurine (probable)

Quartz, SiO₂, with fuchsite mica inclusions

Red Granite

Phaneritic Felsic Intrusive Igneous Rock (primarily K-feldspar, Quartz, and Biotite)

Quartz (Iron-stained)

Silicon Dioxide (SiO2)

Petrified Wood

Silicified Wood (SiO2)

Pink Granite

Phaneritic Felsic Igneous Rock

Weathered greenish rock fragment

Indeterminate; possibly epidote- or chlorite-bearing altered silicate rock

Tumbled goldstone-like quartz pebble

Likely iron-stained quartz or jasper; exact identification requires testing

Quartzite

Quartzite (SiO2)

Red Granite

Phaneritic Plutonic Rock (High Potassium Feldspar)

Chert (Green River Chert)

Microcrystalline Quartz (SiO2)

Dalmatian jasper

Orbicular microcrystalline quartz rock, commonly rhyolitic or volcanic-feldspar matrix with black arfvedsonite/alkali-amphibole inclusions

Small metallic meteorite-like specimen

Unclassified iron-rich meteorite candidate; possibly an ordinary chondrite or terrestrial slag

Iron Slag

Iron smelting byproduct (Glassy/vesicular silicate)

Green fluorite crystal

Fluorite (calcium fluoride, CaF₂)

Graphite Schist

C (Carbonaceous Schist)