Igneous And Metamorphic Derivative (Weathered)

Weathered quartz-rich rock, possibly granite or quartzite

Indeterminate; likely quartz (SiO₂) with feldspar and minor mica, or quartzite

Foliated metamorphic rock, likely mica schist

Mica schist, mainly quartz–feldspar–mica assemblage

Basalt (Stream-worn Cobble)

Mafic Igneous Rock (primarily Plagioclase and Pyroxene)

Weathered granite or granitic gneiss fragments

Granite; primarily quartz, feldspar, and mica (composition uncertain from image)

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

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

Rounded granite or granitic gneiss cobble

Granite; predominantly quartz, feldspar, and mica (approximate identification)

Galena

Lead Sulfide (PbS)

Biotite mica

Biotite, a potassium-rich mica in the annite–phlogopite series; approximate formula K(Mg,Fe)₃AlSi₃O₁₀(F,OH)₂

Biotite mica (likely)

Biotite, a mica-group mineral; approximate formula K(Mg,Fe)₃AlSi₃O₁₀(F,OH)₂

Rounded granite or granitic gneiss pebble

Granite; mainly quartz, feldspar, and mica, possibly with metamorphic foliation

Granite Pebble

Granite (Phaneritic Igneous Rock)

Weathered granite or granitic gneiss

Granite; chiefly quartz, feldspar, and mica

Raw quartz crystal

Quartz (silicon dioxide, SiO₂)

White Quartz

Quartz (Silicon Dioxide, SiO2)

Quartz

Silicon Dioxide (SiO2)

Rounded gray pebble, likely basalt

Basalt; fine-grained mafic volcanic rock, chiefly plagioclase and pyroxene with possible olivine

Labradorite-bearing gneiss or altered feldspathic rock

Plagioclase-rich gneiss, locally labradorescent; composition likely plagioclase feldspar, quartz, mica, and iron-oxide veining

Quartz–mica metamorphic rock, likely schist

Quartz–muscovite/biotite schist; predominantly SiO₂ quartz with phyllosilicate micas

Weathered schist or gneiss boulder

Micaceous quartz-feldspar schist/gneiss; exact identification is limited by the photograph

Dark mafic rock fragments, possibly basalt

Basalt (fine-grained plagioclase–pyroxene rock), tentative

Red-brown granite or granitic gneiss fragments

Felsic granitoid, chiefly quartz, potassium feldspar, plagioclase, and biotite/hornblende

Basalt cobble

Basalt; predominantly plagioclase, clinopyroxene, and often olivine or iron-titanium oxides

Quartz (Gravel Pebble)

Silicon Dioxide (SiO2)

Slate

Metamorphic Mudstone / Shale

Asphalt aggregate

Human-made bituminous asphalt containing crushed silicate rock aggregate

Banded Agate (Tumbled)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Black Tourmaline (Schorl)

Schorl (NaFe3Al6(BO3)3Si6O18(OH)4)

Citrine

Silicon Dioxide (SiO2) with ferric iron impurities

Black Tourmaline

Schorl (NaFe2+3Al6(Si6O18)(BO3)3(OH)4)

Blue Quartz

Silicon Dioxide (SiO2) with inclusions

Milky quartz-bearing rock

Quartz, silicon dioxide (SiO₂), likely massive milky quartz in a host rock

Milky quartz

Quartz (silicon dioxide, SiO₂)

Weathered quartz-rich stone, likely milky quartz

Quartz (SiO₂), possibly a quartz-rich metamorphic or igneous fragment

Concrete-embedded rock fragment, likely weathered granite or gneiss

Probable granitic silicate assemblage: quartz, feldspar, and dark mica/amphibole

Milky quartz (likely quartz vein fragment)

Quartz, silicon dioxide (SiO₂)

Quartz (Raw Chunk)

Silicon Dioxide (SiO2)

Sapphire in a ring

Corundum (Al2O3)

Porphyritic volcanic rock (likely andesite or basaltic andesite)

Porphyritic andesite/basaltic andesite; mainly plagioclase, pyroxene, and possibly olivine in a fine volcanic groundmass

Likely blue-gray stone, possibly slate or basalt

Indeterminate; candidates include slate (fine-grained metamorphic rock) or basalt (mafic igneous rock)

Mica

Phlogopite or Biotite group (KMg3(AlSi3O10)(F,OH)2 / K(Mg,Fe)3AlSi3O10(OH)2)

Milky quartz vein fragment (likely quartz with minor feldspar/mica)

Quartz, SiO₂; possibly associated feldspar and mica

Milky quartz-rich rock

Quartz (silicon dioxide, SiO₂), likely massive quartz with minor feldspar or host-rock material