Mineralogical Specimen

Sandstone (Quartzite texture)

Arenite (SiO2 secondary)

Concrete-like aggregate surface with embedded rock fragments

Anthropogenic concrete or exposed aggregate; not a natural rock specimen

Quartz-bearing feldspathic rock, possibly pegmatite

Granite/pegmatitic granitic rock; primarily quartz (SiO₂) and feldspar

Quartz Druze on Matrix

Silicon Dioxide (SiO2)

River Stone (likely Mudstone or Siltstone)

Lutite (Clastic sedimentary rock composed of clay and silt-sized particles)

Yellow Quartz or Citrine Quartz

Silicon Dioxide (SiO2)

Quartz Pebble

Silicon Dioxide (SiO2)

Biotite-rich mica schist

Mica schist, dominated by biotite mica (K(Mg,Fe)₃AlSi₃O₁₀(F,OH)₂) with quartz and feldspar

Quartz (Bull Quartz)

Silicon Dioxide (SiO2)

Granitoid (Common Granite/Gneiss)

Granitoid (primarily Quartz [SiO2], Feldspar [KAlSi3O8], and Mica)

Toast

Triticum aestivum (processed)

Diamond (in Jewelry)

Diamond (Carbon, C)

Agate / Chalcedony Nodule

SiO2 - Silicon Dioxide

Peacock Ore (Bornite or Iridescent Chalcopyrite)

Bornite (Cu5FeS4) or Acid-treated Chalcopyrite (CuFeS2)

Chert (Polished Gemstone / River Stone)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Milky Quartz

Crystalline Silicon Dioxide (SiO2)

Quartz (Milky or Smoky Quartz)

Silicon Dioxide (SiO2)

Chert (Jasper)

Microcrystalline Quartz (SiO2)

Druzy Quartz on Sandstone

Silicon Dioxide (SiO2) with Quartz Crystals on Clastic Sedimentary Rock

Milky Quartz with Chlorite/Moss Infusions

Silicon Dioxide (SiO2)

Chert / Jasper

Silicon Dioxide (SiO2)

Clear Quartz Crystal Cluster

Silicon Dioxide (SiO2)

Iron-rich stone, likely limonite/goethite-bearing rock

Limonite (hydrated iron oxides; chiefly goethite, FeO(OH), with possible hematite)

Likely quartz-bearing rock fragment

Quartz (SiO₂), possibly with calcite or feldspar

Clear Quartz Crystal on Matrix

SiO2 (Silicon Dioxide)

Quartz (River Cobble)

Silicon Dioxide (SiO2)

Yellow Quartz

SiO2 (Crystalline Silicon Dioxide)

Chert (Jasper variety)

Silicon Dioxide (SiO2)

Chert (Jasper)

Silicon Dioxide (SiO2)

Iron-stained quartz-rich rock, possibly brecciated quartzite or rhyolite

Indeterminate quartz–feldspar rock with iron-oxide staining (SiO₂-rich; possible hematite/goethite)

Granite Pebble

Granite

Milky Quartz with Iron Staining

Silicon Dioxide (SiO2)

Yellow Quartz (Polished)

Silicon Dioxide (SiO2) with iron inclusions

Weathered mica-rich schist

Muscovite–biotite schist, possibly quartz-bearing

Quartz

Silicon Dioxide (SiO2)

Dark coarse-grained rock, likely gabbro or amphibolite

Gabbro (plutonic mafic rock; mainly plagioclase and pyroxene), possibly amphibolite if metamorphosed

Gray metamorphic rock, likely gneiss or schist

Quartz–feldspar–mica metamorphic rock; exact identification requires a fresh surface and tests

Weathered gray metamorphic rock, likely phyllite or slate

Micaceous quartz–phyllosilicate rock; commonly quartz + muscovite/illite ± chlorite

Weathered greenish rock fragment

Tentatively altered basalt or serpentinite; exact identification requires testing

Quartz-rich rock, likely milky quartz with iron staining

Mostly quartz (SiO₂); exact rock type cannot be confirmed from the image

Quartz Pebble

Silicon Dioxide (SiO2)

Milky Quartz with Algae/Iron Staining

Silicon Dioxide (SiO2)