Mineralogical Glass

Tektite (Indochinite)

Tektite (High-silica natural glass)

Flint or chert fragment

Microcrystalline quartz (SiO₂), commonly termed chert or flint

Small tumbled stone, likely quartz-rich pebble

Probably microcrystalline quartz (SiO₂), but the image is insufficient for a definitive identification

Polished purple chalcedony (likely lavender agate)

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

Unidentified purple mineral fragment

Possibly amethyst (quartz), but the image is insufficient for confident identification

Yellow chalcedony (likely dyed or heat-treated)

Microcrystalline quartz, SiO₂ (chalcedony)

Sand Grain (Quartz)

Silicon Dioxide (SiO2)

Uncertain dark gray-brown rock fragment

Indeterminate; possibly weathered chert, serpentine, or iron-stained quartzite

Black-and-white spotted jasper (likely dalmatian jasper), polished beads

Commercially called Dalmatian jasper; typically a feldspar-rich rock with dark inclusions, not true jasper (microcrystalline quartz). Exact composition cannot be confirmed from the image.

Tumbled green jasper or serpentine

Jasper: microcrystalline quartz (SiO₂); possible serpentine: Mg₃Si₂O₅(OH)₄

Painted beach pebble

Unidentified natural pebble; underlying lithology cannot be determined from the image

Tumbled orange chalcedony and a gray stone disk

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

Tumbled green aventurine (probable)

Quartz (SiO₂), commonly with fuchsite mica inclusions

Mixed mineral and shell specimen assortment

Primarily unidentified quartz-/feldspar-like pebbles with possible dark basalt or iron-rich fragments; white pieces may include shell or calcite

Quartzite

Quartzite (primarily SiO2)

Amazonite-bearing feldspar (likely raw amazonite)

Amazonite, a blue-green variety of microcline feldspar; KAlSi₃O₈

Raw ruby (likely corundum)

Corundum, Al₂O₃; red varieties are ruby

Potassium feldspar

Orthoclase or microcline; KAlSi₃O₈

Pistachio-green and dark mineral-bearing rock, possibly serpentine with dark inclusions

Undetermined; the image is insufficient for reliable species-level identification

Blue-gray tumbled stone, likely labradorite or blue-gray feldspar

Plagioclase feldspar, possibly labradorite (NaAlSi₃O₈–CaAl₂Si₂O₈)

Dalmatian jasper (often sold as Dalmatian stone)

Quartz-bearing microgranular felsic rock, commonly an altered rhyolite or related volcanic rock with black aegirine/arfvedsonite-group inclusions

Manganese Dendrite on Siltstone

Manganese Oxide (pyrolusite or psilomelane) Dendrites

Pyrite Sun (Pyrite Dollar)

Iron Disulfide (FeS2)

Iron-stained metamorphic rock, likely schist or quartzite

Quartz–mica–iron oxide rock; probable muscovite/biotite schist or ferruginous quartzite

Tumbled gray chalcedony or quartz pebble

Microcrystalline quartz (SiO₂), possibly gray chalcedony

Citrine

Silicon Dioxide (SiO2)

Blue glass-like tumbled specimen

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

Snowflake Obsidian

Volcanic Glass with Cristobalite inclusions

Tumbled greenstone (probable serpentinite)

Serpentinite, chiefly serpentine-group minerals (Mg₃Si₂O₅(OH)₄), possibly with chlorite, magnetite, or talc

Tiny rounded brown mineral grain

Indeterminate; possibly iron oxide, garnet, or a weathered sulfide grain

Quartz-rich breccia or vein quartz with iron staining

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

Quartzite

Quartzite (SiO2)

Flint or chert

Microcrystalline quartz (SiO₂), likely gray chert/flint

Weathered brown rock fragment, possibly iron-rich sandstone or altered basalt

Indeterminate; likely an iron-oxide–stained silicate rock

Sandstone

Clastic sedimentary rock (primarily SiO2)

Polished banded calcite/aragonite tower

Calcite (CaCO₃), possibly aragonite (CaCO₃)

Quartz-rich metamorphic rock, likely quartzite

Quartzite; predominantly crystalline SiO₂, possibly with mica or feldspar

Dalmatian jasper (likely orbicular microgranite)

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

Dendritic Quartz

Silicon Dioxide (SiO2) with Manganese Oxide inclusions

Weathered quartz-rich pebble

Likely granitic or feldspathic clast; chiefly quartz (SiO₂) and feldspar

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

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

Brown chert or flint pebble

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