Schaff's Bible Dictionary
SAR'DINE, Rev 4:3, or SAR'DIUS, Ex 28:17, a gem of a blood-red or flesh color, susceptible of a high polish, and also called "sard" or "carnelian." Its former name it obtains from Sardis, in Asia Minor, where it was first found. This stone has long been a favorite for the engraver's art. "On this stone all the finest works of the most celebrated artists are to be found; and this not without good cause, such is its toughness, facility of working,
beauty of color, and the high polish of which it is susceptible, and which Pliny states that it retains longer than any other gem." - King: Antique Gems.