Anthropogenic (Man Made)

Granite

Intrusive Igneous Rock (composed primarily of quartz, alkali feldspar, and plagioclase)

Quartz

Quartz (SiO₂)

Porphyritic Basalt or Diabase with Plagioclase Phenocrysts

Porphyritic Basalt or Diabase; Mineral: Plagioclase Feldspar

Ferruginous Sandstone

Sandstone, Iron-rich

Chert Pebble

Microcrystalline Quartz (SiO2)

Granite

Granite (composed primarily of silica-rich minerals like quartz and feldspar)

Limestone

Calcium Carbonate (CaCO3)

Granite

Plutonic felsic igneous rock

Granite

Felsic intrusive igneous rock

Granite

Felsic Plutonic Rock

Granite

Felsic Intrusive Igneous Rock

Granite

Granite (Phaneritic Igneous Rock)

Granite Pebble

Igneous Intrusive Rock (Quartz-Feldspar-Mica Phenocrysts)

Olivine in Basalt matrix

Peridotite (Mg, Fe)2SiO4

Brown Sandstone Pebble

Clastic Sandstone (SiO2 with iron oxides)

Granite

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

Milky Quartz Pebble

Crystalline Silicon Dioxide (SiO2)

Granite

Felsic Plutonic Rock (Granite)

Chert (Quartz Variety)

Chert (Silicon Dioxide, SiO2)

Chert (Flint)

Microcrystalline Silica (SiO2)

Coarse-grained mica-bearing metamorphic rock, likely schist

Mica schist, probably muscovite–biotite schist with quartz and feldspar

Dark fine-grained rock, likely basalt

Basalt; chiefly plagioclase feldspar and pyroxene, commonly with olivine and iron oxides

Black basalt fragment

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

Apatite

Ca5(PO4)3(F,Cl,OH)

Limestone Gravel

Sedimentary Calcium Carbonate (CaCO3)

Granite

Phaneritic plutonic rock (Quartz-Alkali Feldspar-Plagioclase)

Granite

Felsic Plutonic Rock (primarily SiO2)

Granite

Phaneritic plutonic rock (Quartz + Feldspar + Mica)

Granite

Phaneritic Igneous Rock (primarily Quartz, Feldspar, Mica)

Vesicular volcanic rock, possibly weathered basalt or scoria

Basaltic scoria/vesicular basalt; predominantly plagioclase, pyroxene, and iron-titanium oxides

Rounded basalt pebble

Basalt; fine-grained mafic volcanic rock, chiefly plagioclase and pyroxene with minor olivine or magnetite

Granite

Plutonic felsic igneous rock

Granite

Phaneritic plutonic rock (SiO2-rich)

Granite

Plutonic felsic igneous rock

Granite

Granite (Felsic Plutonic Rock)

Granite

Granite (Phaneritic Quartz-Feldspar Plutonic Rock)

Limestone with Fossil Inclusion

Sedimentary Calcium Carbonate (CaCO3)

Granite

Phaneritic Felsic Igneous Rock

Quartz

Quartz (SiO₂ - Silicon Dioxide)

Calcite

Calcite (CaCO3)

Polished white chalcedony or milky quartz pebble

Chalcedony, microcrystalline quartz (SiO₂), possibly with iron-oxide staining or a minor mineral inclusion

Turquoise

Turquoise (Hydrated copper aluminum phosphate, CuAl6(PO4)4(OH)8·4H2O)