Rock & Mineral Encyclopedia

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

Quartzite

An extremely hard metamorphic rock formed from sandstone, made of fused quartz grains that break across rather than between the grains.

A tough, quartz-rich sandstone cemented by silica, transitional toward true quartzite but still sedimentary in origin.

A hard, tough metamorphic rock of fused quartz grains, formed by recrystallizing quartz sandstone under heat and pressure.

A metamorphosed banded iron formation of alternating quartz and iron-oxide layers, mined as a major iron ore.

A coarse sedimentary rock of rounded pebbles and gravel cemented in a finer matrix, recording ancient rivers and beaches.

A conglomerate altered by heat and pressure, often with its rounded pebbles stretched and flattened into elongated lenses.

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

Sandstone altered by metamorphism, with partly recrystallized quartz grains, transitional between true sandstone and quartzite.

An opaque, snow-white variety of quartz whose milky color comes from countless tiny gas and fluid inclusions.

A green quartz speckled with shimmering fuchsite mica that produces a glittering aventurescence, popular as an affordable ornamental stone.

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

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

A metamorphic rock made chiefly of manganese-rich spessartine garnet and quartz, formed from ancient manganese-bearing sediments.