Rock & Mineral Encyclopedia

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

Metabasalt

Basalt that has been metamorphosed, developing new minerals like chlorite, actinolite, and epidote that give it a greenish color.

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

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

A high-grade metamorphic rock defined by alternating light and dark mineral bands, formed under intense heat and pressure.

A feldspar-rich sandstone, often pink, that points to granitic source rocks eroded quickly in dry or cold climates.

A 'mixed rock' showing swirling light and dark bands, formed where high-grade metamorphism causes rock to begin partially melting.

A green-and-white banded metamorphic marble whose wavy mica layers resemble the rings of a sliced onion.

A dark, dense metamorphic rock dominated by hornblende and plagioclase, formed by medium- to high-grade metamorphism of basalt.

A warmly colored chalcedony agate with reds, oranges, golds, and pinks that blend like the glowing bands of a sunset sky.

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

Obsidian formed from two merged lava flows, producing a stone with two distinct bands of sheen or color.

A foliated schist threaded with black tourmaline (schorl) needles, marking boron-rich metamorphic or metasomatic conditions.