Rock & Mineral Encyclopedia

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

Rhyolite

A fine-grained, silica-rich volcanic rock that is the extrusive equivalent of granite, often pale, banded, or flow-textured.

The most abundant mineral group in Earth's crust, feldspars are aluminosilicates that form much of granite and many igneous rocks.

A common rock-forming potassium feldspar, the Mohs hardness reference at 6, found in granites and used in ceramics and glassmaking.

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

An extremely rare rubidium-dominant alkali feldspar, the rubidium analogue of microcline, found in rare-element granitic pegmatites.

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