Anthropogenic (Man Made)

Olivine in Basalt matrix

Peridotite (Mg, Fe)2SiO4

Weathered sandstone boulder

Sandstone, chiefly quartz (SiO₂) with feldspar and iron-oxide cement

Tumbled dark mineral on a polished brown stone slab

Likely quartz-rich chalcedony or jasper slab with a dark metallic mineral inclusion; exact identification is uncertain from the photograph

Limestone

Calcium Carbonate (CaCO3)

Granite

Plutonic felsic igneous rock

Chert (Quartz Variety)

Chert (Silicon Dioxide, SiO2)

Basalt

Mafic volcanic rock, chiefly plagioclase feldspar, pyroxene, and commonly olivine

Rounded basalt cobble

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

Limestone Gravel

Sedimentary Calcium Carbonate (CaCO3)

Dark mafic rock, likely basalt

Basalt; chiefly plagioclase feldspar, pyroxene, and commonly olivine or iron-titanium oxides

Greenstone (likely serpentinite or greenstone pebble)

Serpentinite-rich ultramafic rock; commonly dominated by serpentine-group minerals, with possible chlorite, actinolite, or magnetite

Dark fine-grained rock, likely basalt

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

Weathered limestone fragment, possibly fossiliferous

Calcite-rich limestone (CaCO₃); exact identification is uncertain from one image

Black basalt fragment

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

Apatite

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

Granite

Felsic Plutonic Rock (primarily SiO2)

Granite

Phaneritic plutonic rock (Quartz-Alkali Feldspar-Plagioclase)

Granite

Phaneritic plutonic rock (Quartz + Feldspar + Mica)

Granite

Phaneritic Igneous Rock (primarily Quartz, Feldspar, Mica)

Tumbled milky quartz

Quartz (silicon dioxide, SiO₂)

Quartz

Quartz (SiO₂ - Silicon Dioxide)

Mica-rich metamorphic rock, likely phyllite or schist

Quartz–mica schist/phyllite; chiefly muscovite or biotite mica with quartz and feldspar

Likely polished dark gemstone cabochon

Indeterminate; possibly black chalcedony/agate, obsidian, or glass imitation

Basalt

Basalt; fine-grained mafic volcanic rock composed mainly of plagioclase feldspar, pyroxene, and commonly olivine

Dark basaltic rock fragment

Basalt, likely vesicular or weathered basalt; chiefly plagioclase, pyroxene, and possible olivine

Vesicular basalt (likely weathered volcanic rock)

Basalt; primarily plagioclase feldspar, pyroxene, and possible olivine

Basalt

Mafic volcanic rock, chiefly plagioclase feldspar, pyroxene, and commonly olivine or magnetite

Brown Sandstone Pebble

Clastic Sandstone (SiO2 with iron oxides)

Pink granite (likely weathered)

Granite; predominantly quartz, potassium feldspar, plagioclase, and mica

Granite

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

Milky Quartz Pebble

Crystalline Silicon Dioxide (SiO2)

Granite

Felsic Plutonic Rock (Granite)

Ferruginous Sandstone

Sandstone, Iron-rich

Mixed polished gemstone bead bracelet, likely tourmalinated quartz and rhyolite/jasper

Quartz (SiO₂) with black tourmaline (schorl, NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄) and probable feldspar-rich rhyolite/jasper

Weathered basalt (probable)

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

Likely basalt fragments

Basalt, chiefly plagioclase feldspar and pyroxene, with possible olivine or iron oxides

Granite

Granite (composed primarily of Quartz, Feldspar, and Mica/Amphibole)

Rounded gray pebble, likely basalt

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

Blue Apatite

Fluorapatite (Ca5(PO4)3F)

Granite

Phaneritic Igneous Rock (Granite)

Granite

Course-grained intrusive igneous rock

Diabase (also known as Dolerite)

Diabase / Dolerite