(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.