Rock & Mineral Encyclopedia

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

Tourmalinated Quartz

Clear or milky quartz threaded with black needles of tourmaline (schorl), combining quartz clarity with dramatic dark inclusions.

A treated chalcedony with a network of crackled veins, usually heated and dyed in vivid colors for affordable, eye-catching beads.

The most common variety of quartz, milky white from microscopic fluid and gas inclusions, forming massive veins worldwide.

The smoky brown to gray variety of quartz, colored by natural irradiation, valued as both a gemstone and crystal specimen.

The darkest, near-opaque black variety of smoky quartz, colored by natural radiation acting on trace aluminum.

A foliated metamorphic rock dominated by quartz with enough mica to give it a schistose, splitting fabric.

The pure, colorless form of crystalline quartz, valued for its clarity, abundance, and piezoelectric properties used in electronics.

Clear or smoky quartz threaded with golden to reddish needles of rutile, also poetically called Venus hair stone.

A green, gold-associated metamorphic rock made of chrome-rich mica and quartz, named for Mariposa County in California's gold country.

Clear quartz mined in the Himalayan region, often double-terminated and containing dark hematite or carbon inclusions.

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

Agate that forms in flat cracks or veins of host rock rather than rounded nodules, producing straight, parallel banding.

Natural emerald crystals still embedded in their host rock, prized as mineral specimens that show how the gem grew in place.