From The Collaborative International Dictionary of English v.0.48:
Gem \Gem\, n. [OE. gemme precious stone, F. gemme, fr. L. gemma a precious stone, bud.] 1. (Bot.) A bud. [1913 Webster]
From the joints of thy prolific stem A swelling knot is raised called a gem. --Denham. [1913 Webster]
2. A precious stone of any kind, as the ruby, emerald, topaz, sapphire, beryl, spinel, etc., especially when cut and polished for ornament; a jewel. --Milton. [1913 Webster]
3. Anything of small size, or expressed within brief limits, which is regarded as a gem on account of its beauty or value, as a small picture, a verse of poetry, a witty or wise saying. [1913 Webster]
Artificial gem, an imitation of a gem, made of glass colored with metallic oxide. Cf. Paste, and Strass. [1913 Webster]
From The Collaborative International Dictionary of English v.0.48:
Gem \Gem\ v. t. [imp. & p. p. Gemmed; p. pr. & vb. n. Gemming] 1. To put forth in the form of buds. "Gemmed their blossoms." [R.] --Milton. [1913 Webster]
2. To adorn with gems or precious stones. [1913 Webster]
3. To embellish or adorn, as with gems; as, a foliage gemmed with dewdrops. [1913 Webster]
England is . . . gemmed with castles and palaces. --W. Irving. [1913 Webster]