Easton's Bible Dictionary

Ruby - (Heb. peninim), only in plural (Lam. 4:7). The ruby was one of the stones in the high priest's breastplate (Ex. 28:17). A comparison is made between the value of wisdom and rubies (Job 28:18; Prov. 3:15; 8:11). The price of a virtuous woman is said to be "far above rubies" (Prov. 31:10). The exact meaning of the Hebrew word is uncertain. Some render it "red coral;" others, "pearl" or "mother-of-pearl."