Rock & Mineral Encyclopedia

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

Asphalt Rock

A porous sedimentary rock naturally saturated with bitumen, dark, tarry-smelling, and historically mined for paving.

A dense, black, mid-rank coal with high energy content, widely used for power generation and to make coke for steelmaking.

A dark, organic-rich shale loaded with kerogen and bitumen that can yield oil and gas, often finely laminated and combustible.

A combustible black sedimentary rock formed from ancient plant matter and burned for centuries as a primary fossil fuel.

A fine-grained sedimentary rock rich in solid organic matter (kerogen) that yields oil and gas when heated.

Dark, organic-rich fine-grained sedimentary rock formed in oxygen-poor waters, often a source rock for oil and gas.

A single beryl crystal showing two distinct color zones, such as aquamarine blue grading into morganite pink, within one stone.

Tourmaline displaying two distinct colors in a single crystal, a natural color-zoning effect that makes each stone unique.

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 natural bicolor quartz that combines purple amethyst and golden citrine in a single crystal.

A striking color-zoned tourmaline with a pink center and green rind, resembling a slice of watermelon when cut across the crystal.

Tourmaline crystals displaying two or more distinct colors at once, including the famous pink-and-green watermelon variety.