Rock & Mineral Encyclopedia

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

Siderite

Siderite is an iron carbonate ore, a brown rhombohedral mineral of the calcite group found in sediments and veins.

A rounded sedimentary nodule cracked internally and filled with veins of yellow calcite, prized for its striking dragon-skin patterning.

A historic name for the red-violet to purplish lithium tourmaline first prized from Siberia, closely tied to the rubellite variety.

An iron-rich sedimentary rock, often heavy and rusty-weathering, historically mined as a major source of iron ore.

Small ironstone concretions from Yowah, Queensland, whose hollow or veined centers hold brilliant precious boulder opal.

An opaque grey-brown common opal forming nodules and concretions, historically called liver opal for its dull brownish color.

Elbaite tourmaline in violet to purple hues colored by manganese, a relatively scarce and sought-after tourmaline color.

A purplish, plum-toned elbaite tourmaline colored by manganese, blending the red of rubellite with violet-blue undertones.

An uncommon purple to violet tourmaline colored by manganese, the deeper reddish-purple stones sometimes called siberite.

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