Mineral With Artificial Coating

Weathered basalt or mafic volcanic rock

Basalt; predominantly plagioclase feldspar, pyroxene, and commonly olivine or iron oxides

Quartz (Iron-stained Quartz)

Silicon Dioxide (SiO2)

Quartz (Iron-Stained)

Silicon Dioxide (SiO2)

Iron-rich weathered stone, possibly limonite/goethite

Limonite (mixture of hydrated iron oxides), commonly goethite (α-FeO(OH))

Cobaltite or cobalt-bearing calcite specimen

Likely erythrite (hydrated cobalt arsenate), Co₃(AsO₄)₂·8H₂O

Rough Diamond

Diamond (C)

Chert (Flint with Iron Staining)

Silicon Dioxide (SiO2)

Iron-stained quartz vein rock

Milky quartz (SiO₂) with limonite/goethite iron oxides, possibly in altered host rock

Quartz Druze on Matrix

Silicon Dioxide (SiO2)

Iron-stained quartz cluster

Quartz (SiO₂), likely with limonite/goethite staining and possible feldspar matrix

Native copper-bearing sulfide specimen

Likely chalcopyrite (CuFeS₂), possibly with native copper and iron oxides

Iron-Stained Quartz

Silicon Dioxide with Iron Oxide (SiO2 with Fe2O3)

Iron-rich weathered pebble

Likely limonite/goethite-bearing ferruginous rock; exact identification requires testing

Milky quartz (quartz-rich fragment)

Quartz, silicon dioxide (SiO₂)

Mosasaur Tooth

Mosasaurus sp.

Weathered volcanic rock, likely andesite or basalt

Fine-grained mafic to intermediate volcanic rock; likely basaltic andesite/andesite, composition dominated by plagioclase with pyroxene and/or olivine

Basalt with Desert Varnish

Mafic Igneous Rock with Ferromanganese Coating

Pyrite

Iron Disulfide (FeS2)

Chert (Jasper variation)

Microcrystalline Quartz (SiO2)

Milky quartz (possible pale green quartz)

Quartz, silicon dioxide (SiO₂)

Amethyst (purple quartz), likely with quartz matrix

Quartz, silicon dioxide (SiO₂), purple variety colored mainly by iron-related impurities and irradiation

Milky quartz

Quartz (silicon dioxide, SiO₂)

Raw citrine quartz point

Quartz, SiO₂; yellow coloration likely from iron impurities or heat treatment

Amethyst cluster

Quartz, silicon dioxide (SiO₂), purple variety colored mainly by iron impurities and irradiation

Galena-bearing quartz rock

Galena (PbS) in quartz gangue, likely with minor sulfides and iron oxides

Tourmalinated quartz crystal point

Quartz (SiO₂) with black tourmaline (schorl, NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄) inclusions

Ironstone Concretion (Moqui Marble / Boji Stone)

Sedimentary Iron Oxide Concretion (Fe2O3 / FeO(OH))

Quartz Pebble (Iron-Stained Quartz)

Silicon Dioxide (SiO2)

Tumbled milky quartz pebble

Quartz, silicon dioxide (SiO₂)

Limonite (Iron Ore)

Limonite (FeO(OH)·nH2O)

Weathered sandstone fragment

Quartz-rich sandstone, likely arkose or lithic sandstone

Tiger's Eye

Pseudomorph of quartz after crocidolite (SiO2)

Likely weathered basalt or vesicular volcanic rock

Basalt, composed mainly of plagioclase feldspar, pyroxene, and minor olivine/iron oxides

Titanium Aura Quartz (Bismuth-coated Druzy)

Silicon Dioxide (SiO2) with Titanium/Metal vapor coating

Ferruginous Quartz (Iron-stained Quartz)

Silicon Dioxide (SiO2) with Hematite/Limonite impurities

Dyed Dalmatian Jasper (Dalmatian Stone)

Perthitic Feldspar with Arfvedsonite inclusions

Fossilized Shark Tooth

Elasmobranchii (tooth fossil, composed mainly of Bioapatite / Calcium Phosphate)

Clear quartz crystal

Quartz (silicon dioxide, SiO₂)

Likely iron-stained quartz/chalcedony pebble

Silicon dioxide (SiO₂), probably quartz or microcrystalline chalcedony with iron-oxide staining

Unidentified rough mineral/rock fragment

Indeterminate from image; possibly quartz-rich material or weathered carbonate rock

Limonitic Iron Ore / Goethite

Hydrated Iron(III) oxide-hydroxide (primarily FeO(OH)·nH2O)

Aura Quartz (Titanium-coated Quartz)

Silicon Dioxide (SiO2) with metallic vapor coating