Emerald

Emerald - (Easton's Bible Dictionary)

Heb. nophek (Ex. 28:18; 39:11); i.e., the "glowing stone", probably the carbuncle, a precious stone in the breastplate of the high priest. It is mentioned (Rev. 21:19) as one of the foundations of the New Jerusalem. The name given to this stone in the New Testament Greek is smaragdos, which means "live coal."

Emerald - (Webster's 1828 Dictionary)

EM'ERALD, n. [L. smaragdus.] A mineral and a precious stone, whose colors are a pure, lively green, varying to a pale,yellowish, bluish, or grass green. It is always crystallized, and almost always appears in regular, hexahedral prisms, more or less perfect, and sometimes slightly modified by truncations on the edges, or on the solid angles. It is a little harder than quartz, becomes electric by friction, is often transparent, sometimes only translucent, and before the blowpipe is fusible into a whitish enamel or glass. The finest emeralds have been found in Peru.

The subspecies of emerald are the precious emerald and the beryl.