ulexite

Plural: ulexites

Noun

• A white fibrous mineral, a hydrated sodium calcium borate.
• A white mineral with triclinic crystals, NaCaB₅O₉·8H₂O, noted for its fibers which transmit light by internal reflection, such that a piece with flat faces perpendicular to the fibers' orientation displays an image of whatever is adjacent to its other side.

Examples

• Finding ULEXITE on his rack felt like unearthing a rare geological gem.