EASTON’S BIBLE DICTIONARY (1897 EDITION)
Agate – (Heb. shebo), a precious stone in the breast-plate of the high priest (Ex. 28:19; 39:12), the second in the third row.
This may be the agate properly so called, a semi-transparent crystallized quartz, probably brought from Sheba, whence its name.
In Isa. 54:12 and Ezek. 27:16, this word is the rendering of the Hebrew cadcod, which means “ruddy,” and denotes a variety of minutely crystalline silica more or less in bands of different tints.
This word is from the Greek name of a stone found in the river Achates in Sicily.