Unknown (Likely Sedimentary Or Metamorphic)

Banded sandstone or quartzite fragment

Quartz-rich sandstone; possibly weakly metamorphosed quartzite

Likely weathered metamorphic rock (possibly schist or gneiss)

Indeterminate; probable mica-rich quartz–feldspar metamorphic rock

Weathered metamorphic rock, likely schist or gneiss

Quartz–feldspar–mica metamorphic rock; exact identification requires testing

Foliated metamorphic rock, likely biotite schist

Mica schist, chiefly quartz, feldspar, and biotite mica

Mica-rich schist (likely biotite–muscovite schist)

Mica schist; composed chiefly of muscovite and/or biotite with quartz and feldspar

Likely weathered limestone or calcitic marble

Calcite-rich carbonate rock; chiefly calcium carbonate, CaCO₃

Red coral (polished coral beads)

Corallium spp.; chiefly calcium carbonate (CaCO₃, calcite)

Dark metamorphic pebble, likely slate or phyllite

Slate/phyllite; chiefly fine-grained mica and quartz, with possible chlorite and graphite

Dark, mica-rich metamorphic rock (possibly schist)

Mica schist, tentatively; exact identification is limited by the small, partly obscured specimen

Iron-rich sulfide ore (likely pyrite-bearing rock)

Likely pyrite (FeS₂) with dark host rock; exact identification is uncertain from the image alone.

Possibly biotite-rich schist

Mica schist, composed mainly of quartz and mica (often biotite); exact identification is uncertain from the photo.

Red aventurine quartzite (likely)

Quartzite; predominantly microcrystalline quartz (SiO₂) with iron-oxide and feldspar impurities

Quartz-rich metamorphic fragment (likely mica schist)

Mica schist, probably muscovite–quartz schist

Felsic gneiss, likely granitic gneiss

Quartz–feldspar–mica gneiss; commonly quartz + plagioclase/K-feldspar + biotite or hornblende

Quartz-rich river pebble, likely milky quartz

Milky quartz (SiO₂), possibly a quartzite or quartz-rich silicate pebble

Polished gemstone tower assortment

Primarily quartz varieties and simulants; apparent amethyst (SiO₂), rose quartz (SiO₂), clear quartz (SiO₂), fluorite (CaF₂), sodalite, malachite, and possibly dyed or composite stones

Dark rock specimen (possibly slate or shale)

Unidentified fine-grained rock; slate is foliated metamorphosed shale, while shale is sedimentary mudrock

Small gold-colored mineral crystal, likely pyrite

Pyrite (FeS₂), tentatively; native gold is a less likely alternative

Blue-gray calcite (likely cleavage specimen)

Calcite, CaCO₃

Quartz-bearing metamorphic rock, likely schist or quartzite

Quartz (SiO₂) in a mica-rich metamorphic matrix

Banded metamorphic rock, likely banded gneiss

Gneiss, probably biotite–quartz–feldspar gneiss

Rounded gray metamorphic pebble, likely gneiss or granitic rock

Probable quartz–feldspar–mica gneiss; exact identification requires a fresh surface and testing

Likely clear quartz fragment

Quartz (SiO₂)

Likely milky quartz fragment

Quartz (SiO₂)

Granite Gneiss with Garnet

Garnetiferous Gneiss

Pyrite (likely)

Iron disulfide, FeS₂; commonly called fool’s gold

Likely gray sandstone or fine-grained metamorphic rock

Quartz-rich lithic sandstone; exact identification is uncertain from the photograph

Quartz Vein in Siltstone

Silicon Dioxide (SiO2) within Sedimentary/Metamorphic Matrix

Weathered schist or gneiss cobble

Foliated silicate rock, likely mica schist or biotite gneiss

Quartzite with Chert inclusions

Metamorphosed Quartz-rich Rock (SiO2)

River Stone (Quartzite/Chert)

Metamorphosed Quartz-rich Sedimentary Rock

Likely mica schist

Mica-rich schist, probably muscovite/biotite schist with quartz and feldspar

Clear quartz fragment

Quartz (silicon dioxide, SiO₂)

Weathered quartz-rich pebble, possibly quartzite or chert

Quartz (SiO₂), possibly quartzite; exact identification is uncertain from the image

Banded metamorphic rock, likely mica schist

Mica schist, chiefly quartz, muscovite/biotite, and feldspar

Weathered gray metamorphic rock, likely slate or phyllite

Fine-grained foliated metamorphic rock; commonly quartz–mica–chlorite, possibly chlorite phyllite

Weathered metamorphic rock, likely schist or slate

Foliated pelitic metamorphic rock; commonly muscovite–chlorite schist or phyllite

Likely chlorite schist

Chlorite-rich schist; commonly composed of chlorite, quartz, and mica

Milky quartz in a weathered host rock

Quartz (SiO₂), with an unidentified fine-grained matrix

Likely weathered gneiss

Foliated metamorphic rock, commonly quartz–feldspar–mica gneiss

Quartz-veined metamorphic rock, likely schist or gneiss

Micaceous quartz-feldspar rock; probable mica schist/gneiss with quartz veins

Coarse-grained metamorphic rock, likely gneiss

Biotite–quartz–feldspar gneiss (tentative; exact identification requires testing)