(Heb. wb#), a precious stone in the breast-plate of the high priest (Exodus 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 Isaiah 54:12 and Ezekiel 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.
These dictionary topics are from M.G. Easton M.A., D.D., Illustrated Bible Dictionary, Third Edition, published by Thomas Nelson, 1897. Public Domain, copy freely.
Easton, Matthew George. "Entry for 'Agate'". "Easton's Bible Dictionary".