A mineral occurring in minute prisms, either single or adhering to each other in fascicular groups. Before the blowpipe, it melts with ebullition or intumescence, and its powder on hot coals phosphoresces with a feeble light. Its name, from Gr., two; fire, indicates the double effect of fire, in producing fusion and phosphorescence.

A mineral of the scapolite group; -- so called from the double effect of fire upon it, in fusing it, and rendering it phosphorescent.

Containing two stones or nutlets.