Rock & Mineral Encyclopedia

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

Banded Iron Formation

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

An opaque green variety of chalcedony quartz colored by iron and chlorite-group inclusions, prized as a durable carving and cabochon stone.

A dark green jasper-chalcedony speckled with red iron-oxide spots, classically known as bloodstone or heliotrope.

A microcrystalline quartz jasper marked by small concentric ring or eye patterns that resemble the eyes of birds.

A jasper made of angular fragments naturally cemented back together, typically showing red and brown pieces in a quartz matrix.

A banded, metamorphosed iron formation in which bright red jasper alternates with silvery hematite or magnetite layers.