Rock & Mineral Encyclopedia

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

Orbicular Granite

A rare granitic rock containing concentric, onion-like spheres called orbicules, prized as a striking ornamental stone.

A granite-like rock containing orthopyroxene, formed at high temperatures and pressures and often classed with the granulites.

A common coarse-grained intrusive rock like granite but richer in plagioclase than potassium feldspar.

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

Rounded nodules of translucent obsidian, named after a Native American legend, that glow smoky brown when held to light.

A pale translucent chalcedony threaded with brown-black manganese and iron dendrites that mimic tiny ferns, mosses or landscapes.

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

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

A lithified glacial till, a poorly sorted rock of mixed boulders, pebbles and fine matrix that records ancient glaciations.

Glacially deposited banded agates found along Lake Michigan beaches, small waterworn pebbles with concentric red and grey banding.

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

A hydrated volcanic glass with pearly, onion-like concentric cracks that pops into lightweight white granules when heated.