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

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

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

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

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

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

Glacially transported banded agates found along Lake Huron's shores, typically small, frosted pebbles with red-orange iron banding.