sedimentary or metamorphic

Sandstone or Quartzite

Sandstone or Quartzite (SiO2 primarily)

Hardness: 6-7 (Mohs), Color: Reddish-brown due to iron oxide staining, Luster: Dull to earthy, Texture: Granular.

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Physical properties

Hardness: 6-7 (Mohs), Color: Reddish-brown due to iron oxide staining, Luster: Dull to earthy, Texture: Granular.

Formed from compressed sand (sedimentary) or metamorphosed sandstone (metamorphic), often heavily weathered by water.

Common rock type, sometimes used as aggregate or in landscaping. This specific piece is a common find and holds little commercial value.

The reddish color is typical of rocks stained by hematite or other iron oxides.

Identified by its granular texture (if sandstone) or extreme hardness and fused grains (if quartzite). Extremely common.

Natural freshwater pearls

Pearl (nacreous calcium carbonate; chiefly aragonite, CaCO₃)

Dark gray rounded river pebble

Likely basalt or fine-grained volcanic rock; exact identification requires testing

Weathered dark stone, possibly basalt

Basalt; commonly plagioclase feldspar, pyroxene, and minor olivine

Painted River Rock

Artificially Coated Sedimentary Rock

Red coral (coral beads)

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

Tumbled milky quartz

Quartz, SiO₂; trigonal crystal system