Igneous, Sedimentary, And Metamorphic

Natural freshwater pearls

Pearl (nacreous calcium carbonate; chiefly aragonite, CaCO₃)

Likely milky quartz

Quartz (silicon dioxide, SiO₂)

Clear quartz crystal pendant

Quartz (silicon dioxide, SiO₂)

Tumbled milky quartz

Quartz, SiO₂; trigonal crystal system

Quartz (likely milky or iron-stained quartz)

Quartz, silicon dioxide (SiO₂)

Milky quartz cluster

Quartz (silicon dioxide, SiO₂)

Tumbled milky quartz

Quartz (silicon dioxide, SiO₂)

Milky quartz crystal cluster

Quartz (silicon dioxide, SiO₂)

Tumbled clear quartz

Quartz (SiO₂)

Tumbled clear quartz

Quartz (silicon dioxide, SiO₂)

Clear quartz (rock crystal)

Quartz, crystalline silicon dioxide (SiO₂)

Milky quartz

Quartz (silicon dioxide, SiO₂)

Red coral (coral beads)

Precious coral, usually Corallium spp.; composed primarily of calcium carbonate (calcite)

Milky quartz

Quartz, silicon dioxide (SiO₂)

Amber (likely a small rough amber piece)

Fossilized plant resin; amber is an organic mineraloid, not a crystalline mineral

Quartz-rich pebble

Mostly quartz (SiO₂), possibly a quartzite or vein-quartz fragment

Yellow chalcedony or quartz fragment

Microcrystalline quartz, SiO₂ (tentative; possibly iron-stained chalcedony)

Polished fossil coral

Fossilized coral, commonly agatized coral (silica replacing CaCO₃)

Silicified oyster fossil

Fossil oyster shell, commonly Ostrea or Crassostrea, replaced or encrusted by chalcedony/quartz

Quartz geode or quartz-bearing rock

Quartz (SiO₂), likely in a chalcedony- or basalt-hosted cavity

Honey-colored quartz cluster

Quartz, silicon dioxide (SiO₂), likely iron-stained or included quartz

Milky quartz-bearing rock, possibly quartzite

Quartz (SiO₂), likely in a quartzite or quartz-rich vein

Fossilized bone fragment (probable mammalian tooth or bone)

Mineralized bone, commonly hydroxyapatite [Ca5(PO4)3(OH)] replaced or impregnated by silica/calcite

Yellow-orange quartz/chalcedony pebble (possibly citrine-bearing)

Quartz, SiO₂; likely microcrystalline chalcedony with iron staining

Baked-clay ceramic fragment (likely brick or pottery)

Fired clay, primarily aluminosilicate minerals; not a natural rock

Polished operculum (“Shiva eye” shell)

Calcium-carbonate shell operculum, commonly from a turban snail (family Turbinidae); not a mineral specimen

Weathered quartz-bearing rock, possibly calcite vein fragment

Indeterminate; likely quartz (SiO₂) with carbonate minerals such as calcite (CaCO₃)

Amethyst and mixed gemstone bracelet

Amethyst: purple quartz, silicon dioxide (SiO₂); likely accompanied by other quartz or decorative mineral beads

Iron-stained milky quartz

Quartz (SiO₂), with reddish-brown iron-oxide staining

Oyster shell fragment

Ostreidae shell; primarily calcite (CaCO₃)

Green chalcedony (possibly chrysoprase) cabochon

Chalcedony, microcrystalline quartz (SiO₂); chrysoprase is nickel-colored chalcedony

Likely quartz-rich rock with white quartz veins or patches

Quartz-bearing rock; exact rock type cannot be determined from the photograph

River Pebbles and Quartz

Mixed Igneous, Sedimentary, and Metamorphic Rocks (Silicon Dioxide SiO2 dominant)

Rock and Mineral Collection

Mixed Geological Specimens

Mixed Tumbled Gemstones

Various silicate and oxide minerals

Mixed Tumbled Gemstones and Minerals

Various silicate and oxide minerals

Gemstone Beads

Various mineral species

Agate

SiO2 (Chalcedony/Quartz)

Clear Quartz

Silicon Dioxide (SiO2)

Zoisite with Rubellite (Ruby in Zoisite)

Zoisite with inclusions of Hornblende (Anyolite)

Clear Quartz

Silicon dioxide (SiO2)

Chalcopyrite

Copper Iron Sulfide (CuFeS2)