Mineraloid (Human Made Geological Specimen)

Travertine

Calcium Carbonate (CaCO3)

Honey Calcite

Calcium Carbonate (CaCO3)

Porphyritic granite (likely weathered granitic rock)

Granite; chiefly quartz, alkali feldspar, plagioclase, and biotite/hornblende

Tumbled zebra stone, likely zebra marble or banded calcite

Zebra marble (recrystallized calcite, CaCO₃), possibly black-and-white banded calcite

Pyrite (on Shale/Matrix)

Iron Disulfide (FeS2)

Chert

Chert (Microcrystalline Quartz, SiO2)

Green Calcite

Calcite (CaCO3)

Quartz Geode

Silicon Dioxide (SiO2)

Tumbled dark pebble

Indeterminate; likely basalt or fine-grained dark metamorphic rock

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Tumbled brown quartz/chalcedony (probable)

Quartz, SiO₂; possibly brown chalcedony or jasper

Green Aventurine

Silicon Dioxide (Quartz with Fuchsite inclusions) - SiO2

Magnetic Hematite

Magnetized Hematite (an iron oxide mineral, Fe2O3, that has undergone magnetization)

Possible iron-rich chert or slag-like rock

Microcrystalline quartz (SiO₂), possibly iron-stained chert; exact identification is uncertain from the image

Granite Cobble

Phaneritic Felsic Igneous Rock (primarily Quartz, Feldspar, and Mica)

Tumbled quartz-rich pebble

Microcrystalline quartz (SiO₂), possibly weathered chert or chalcedony

Biotite (Black Mica)

Biotite - K(Mg,Fe)3AlSi3O10(F,OH)2

Raw Diamond

Carbon (C)

Sandstone

Arenite (primarily SiO2)

Limonite (Ochreous)

FeO(OH)·nH2O (Hydrated Iron Oxide)

Asphalt Chunk (with aggregate)

Bituminous concrete / Anthropogenic conglomerate

Rounded gray river cobble

Likely basalt or fine-grained mafic volcanic rock; exact identification requires testing

Pyrite

Iron Sulfide (FeS2)

Clear quartz crystal point

Quartz (silicon dioxide, SiO₂), likely a polished or cut crystal

Chert (Arrowhead Fragment)

Microcrystalline Quartz (SiO2)

Rounded pale quartz-rich pebble

Likely milky quartz or quartzite (SiO₂); exact identification is uncertain from the photograph

Polished multicolored jasper

Jasper, an opaque microcrystalline variety of quartz (SiO₂), likely iron- and manganese-stained chert

Satin Spar (Selenite)

Gypsum (Calcium Sulfate Dihydrate) - CaSO4·2H2O

Quartz

Silicon Dioxide (SiO2)

Titanium-Coated Hematite (Aura Hematite)

Titanium-bonded Hematite (Fe2O3 with a Ti coating)

Chrysocolla

Hydrated copper phyllosilicate, (Cu,Al)2H2Si2O5(OH)4·nH2O

Milky quartz (rough quartz fragment)

Quartz, silicon dioxide (SiO₂)

White quartzite pebble

Quartzite, composed predominantly of quartz (SiO₂)

Polished brecciated jasper (likely orbicular/picture jasper)

Microcrystalline quartz/chalcedony (SiO₂) with iron-oxide staining and breccia fragments

Biotite schist (likely graphite-bearing)

Mica schist; chiefly quartz + biotite mica, with possible graphite and feldspar

Pyrite

Iron Sulfide (FeS2)

Rough Quartz (likely Rose or Amethyst variety)

Silicon Dioxide (SiO2)

Yellow Jasper

Silicon Dioxide (SiO2) with iron oxide inclusions

Weathered quartz-rich rock, likely silicified limestone or quartzite

Microcrystalline quartz (SiO₂), possibly with calcite (CaCO₃) and iron-oxide staining

Granite

Phaneritic Igneous Rock (primarily Quartz, Feldspar, and Mica)

Chert (specifically Jasper/Carnelian Agate)

Microcrystalline Quartz (SiO2)

Milky quartz with iron-oxide staining and dark matrix

Quartz (SiO₂), likely with hematite/goethite and minor feldspar or mica