Rock & Mineral Encyclopedia

Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.

Chert

A hard, fine-grained sedimentary silica rock that breaks with sharp conchoidal edges, prized by ancient toolmakers.

A hard, fine-grained siliceous rock with a dull porcelain-like texture, intermediate between soft diatomite and dense chert.

A hard, fine-grained siliceous rock built from the microscopic silica skeletons of radiolarians, often forming colorful ribbon-banded cherts.

A hard, dark variety of chert that knaps into razor-sharp edges and sparks against steel, central to Stone Age technology.

A pure, translucent white marble from the Greek island of Paros, the preferred stone of ancient sculptors for its waxy glow.

Ancient chemically deposited rock of alternating iron-oxide and silica bands recording Earth's early oxygenation and a major iron ore source.

The fine white marble of Mount Pentelikon used to build the Parthenon, famous for the golden patina it develops with age.

A fractured fine-grained limestone whose iron-stained crack networks form natural scenes resembling ruined cities and landscapes.

A plume agate whose inclusions form upright, bristly clusters resembling the strokes of a paintbrush.

The green chromium- and vanadium-colored variety of beryl, one of the four classic precious gemstones renowned for its rich green color.

A scenic jasper whose flowing streaks of warm color resemble strokes left by a loaded paintbrush.

Precious opal from the Andamooka field of South Australia, famous for solid crystal opal and its distinctive treatable matrix opal.

A porous sedimentary rock naturally saturated with bitumen, dark, tarry-smelling, and historically mined for paving.

A landscape-patterned Chinese jasper prized for warm cherry-red, cream, and green bands resembling painted scenery.