Mineralogical Specimen

Rounded greenish river pebble

Likely altered basalt or greenstone (metabasalt); exact identification requires testing

Quartz geode

Microcrystalline quartz and crystalline quartz (SiO₂), likely in a weathered volcanic or sedimentary host

Common Opal

SiO2·nH2O (Hydrated Silicon Dioxide)

Polished mahogany obsidian (probable)

Volcanic glass; chiefly rhyolitic silica-rich glass (SiO₂), compositionally near rhyolite

Likely basalt

Basalt; fine-grained mafic volcanic rock, mainly plagioclase and pyroxene, commonly with olivine

Mixed mineral specimens, prominently chalcopyrite and amethyst

Chalcopyrite (CuFeS₂) with secondary copper minerals; amethyst, purple quartz (SiO₂)

Weathered foliated metamorphic rock, likely schist or gneiss

Mica schist to gneiss; commonly quartz + feldspar + biotite/muscovite

Weathered quartz-rich rock, possibly granite or quartzite

Indeterminate; likely quartz-feldspar aggregate, potentially granitic or quartzitic material

Weathered quartz-rich rock, likely sandstone or quartzite

Quartz-dominated clastic rock; possibly quartzite (SiO₂-rich)

Rounded quartz-rich sandstone or quartzite cobble

Quartz-dominated siliciclastic rock; likely sandstone, possibly weakly metamorphosed quartzite

Weathered quartz-rich rock, likely quartzite

Quartzite; predominantly quartz (SiO₂), possibly with feldspar and iron-oxide staining

Basalt

Basalt; primarily plagioclase, pyroxene, and commonly olivine

Fossilized Shark Tooth (Sand Tiger)

Carcharias taurus (fossil specimen)

Dark mafic metamorphic rock, likely amphibolite

Amphibolite; chiefly hornblende amphibole and plagioclase feldspar

Metallic sulfide mineral specimen, likely pyrite

Pyrite (FeS₂), possibly mixed with marcasite or another iron sulfide

Botryoidal hematite (ironstone)

Hematite, Fe₂O₃; likely a botryoidal or massive iron-oxide specimen

Human Skin (Epidermis/Dermis)

Integumentary tissue (High content of hydroxyapatite in bones, though the surface is biological)

Iron-stained quartz-rich rock, possibly weathered granite or quartzite

Indeterminate quartz–feldspar aggregate with iron-oxide staining; likely granitic or hydrothermal material

Rounded river pebbles, likely basalt and sandstone/conglomerate

Probable basalt (dark specimen) and ferruginous sandstone or weathered conglomerate (tan specimen)

Cullet Glass (Slag)

Amorphous Silicon Dioxide (Man-made)

Small polished metallic mineral specimen

Indeterminate from image; possibly galena or hematite

Quartz-rich geode or drusy quartz specimen

Quartz, silicon dioxide (SiO₂), likely coating a carbonate or volcanic-rock cavity

Pyrite specimen

Pyrite, FeS₂ (iron disulfide)

Malachite specimen

Malachite, Cu₂CO₃(OH)₂

Calcite specimen

Calcite (calcium carbonate, CaCO₃), likely botryoidal or drusy calcite

Banded Gneiss

Metamorphic Gneiss (High-grade regional metamorphism specimen)

Milky quartz-bearing rock, possibly quartzite

Quartz (SiO₂), likely in a quartzite or quartz-rich metamorphic matrix

Quartz-rich rock, possibly quartzite

Quartzite (dominantly quartz, SiO₂); identification is provisional from the photo

Likely serpentine and polished hematite

Serpentine-group minerals, commonly antigorite/lizardite; hematite, Fe₂O₃

Aragonite crystal cluster

Aragonite, orthorhombic CaCO₃

Quartz geode (likely amethyst-bearing geode)

Microcrystalline quartz and drusy quartz; SiO₂, with possible iron-stained or amethyst quartz

Likely weathered granite or granitic gneiss fragment

Quartz–feldspar–mica aggregate; possibly granitic gneiss

Fossil brachiopod shell

Brachiopoda; exact genus/species indeterminate

Honey-colored quartz-rich rock, possibly yellow chalcedony or quartzite

Quartz/chalcedony, SiO₂; exact identification is uncertain from the photograph

Dark gray metamorphic rock, likely slate or phyllite

Slate/phyllite; chiefly fine-grained mica, chlorite, quartz, and clay-derived minerals

Shale with Trace Fossils

Fissile mudrock (Shale)

Polished smoky quartz with iron-stained quartz inclusion

Smoky quartz, SiO₂; inclusion likely quartz with iron-oxide staining

Likely slate or fine-grained metamorphic rock

Slate; predominantly microscopic mica, quartz, and clay-derived minerals

Granite

Coarse-grained felsic intrusive igneous rock, mainly quartz, alkali feldspar, plagioclase, and mica

Weathered gray stone fragment

Undetermined; possibly limestone or sandstone

Botryoidal Agate

Silicon Dioxide (SiO2)

Iron-rich laterite or weathered ironstone

Goethite–hematite-bearing ferruginous duricrust; commonly approximated as FeO(OH) and Fe₂O₃