Rock & Mineral Encyclopedia

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

Red Sandstone

Iron-stained sandstone whose red color comes from hematite coatings, formed in oxidizing desert, river, and coastal environments.

Sand-grained limestone composed of carbonate particles such as shell fragments and ooids cemented into a calcite rock.

A fractured fine-grained limestone whose iron-stained crack networks form natural scenes resembling ruined cities and landscapes.

A clean, mature sandstone made almost entirely of quartz grains, representing extreme weathering, sorting, and recycling of sediment.

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

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

A sedimentary rock built from pea-sized concentric spheres called pisoids, often carbonate but sometimes iron or aluminum-rich.

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