Rock & Mineral Encyclopedia

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

Sandstone

A clastic sedimentary rock made of cemented sand grains, often quartz, recording ancient beaches, deserts, and rivers.

A general term for light-colored, fine-grained volcanic rocks rich in quartz and feldspar, like rhyolite.

A fine-grained clastic rock of silt-sized grains, intermediate between sandstone and mudstone, with a gritty feel.

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

The most common sedimentary rock, a fissile mudrock of compacted clay and silt that splits into thin layers.

The fine-grained volcanic equivalent of monzonite, an intermediate lava with nearly equal feldspars and little free quartz.

A fine-grained volcanic rock intermediate between andesite and rhyolite, common at explosive stratovolcanoes.

An Australian green rhyolite with eye-like orbs and earthy patterns marketed as jasper, evoking dense rainforest foliage.

A fine-grained volcanic rock dominated by alkali feldspar, the extrusive equivalent of syenite.

A fine-grained, sodium-rich contact-metasomatic rock formed where shale is albitized next to intruding diabase or spilite.

A fine-grained, feldspar-rich dike rock with a trachytic texture, essentially a hypabyssal equivalent of trachyte or syenite.

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

A coarse-grained intrusive igneous rock dominated by alkali feldspar with little or no quartz.

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

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