Rock & Mineral Encyclopedia

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

Loess

A loose, wind-blown silt deposit, typically buff-colored and very fertile, that forms thick blankets and stands in steep cliffs.

A finely speckled pale jasper trade stone named for its sesame-seed-like flecks, closely related to Kiwi Jasper.

A speckled green-and-black stone resembling kiwi fruit, technically a quartz-amazonite aggregate rather than true jasper.

A vivid yellow-and-black banded stone from Indonesian volcanic vents, colored by sulfur, arsenic minerals and iron oxides, not true jasper.

A striking platy, blade-like variety of albite feldspar that grows in fanned aggregates of thin white crystals within granite pegmatites.

Extremely hard surface rock formed when silica cements soil and sediment into a tough duricrust in arid landscapes.

Carbonate-cemented soil crust formed in arid regions where calcium carbonate accumulates and hardens within the regolith.

A green, glauconite-rich marine sandstone that records slow deposition on continental shelves and is used as a soil amendment.

A gypsum-rich duricrust that forms by evaporation in arid soils, cementing sediment into a hard surface layer in deserts.

A hardened soil crust cemented by calcium carbonate, forming a tough whitish layer common in arid and semi-arid regions.

Hard surface crust formed when iron oxides cement soil and sediment into a rusty, durable duricrust in tropical and weathered terrains.