Fausset's Bible Dictionary
(in English "a little coal," "a bright red gem"): eqedach , boreqeth , the former in Isaiah 54:12 from qadach "to burn," the latter from baraq "to flash." A brightly flashing stone. A smaragd (Septuagint) or corundum, of green glass color, transparent, and doubly refractive; the emerald (Exodus 28:17); third stone in the first row m the high priest's breast-plate (Ezekiel 28:13).
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Fausset, Andrew R. Entry for 'Carbuncle'. Fausset's Bible Dictionary. https://www.studylight.org/dictionaries/eng/fbd/c/carbuncle.html. 1949.