Rock & Mineral Encyclopedia

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

White Opal

The most common precious opal, with a pale milky body that shows softer pastel flashes of play-of-color throughout.

Abundant banded chalcedony from southern Brazil, the world's main source of agate slices and dyed agate products.

Opal from Australia, the world's leading source of precious opal, ranging from white and crystal to prized black and boulder types.

Molybdenite is the primary ore of molybdenum, a soft, greasy, silver-gray sulfide that closely resembles graphite.

A nodular rhyolite geode-like ball whose plain exterior hides a star-shaped agate or chalcedony core when cut.

A hydrated volcanic glass with pearly, onion-like concentric cracks that pops into lightweight white granules when heated.