Rock & Mineral Encyclopedia

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

Seam Agate

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

Precious opal from Spencer, Idaho, occurring in thin colorful seams that are typically cut into triplets.

Opal in which precious play-of-color is intimately dispersed through the pores of its host rock rather than forming a solid seam.