See also Urim and Thummim

The scriptures mention two types of breastplates: (1) The front part of a soldier’s protective clothing or armor. In a symbolic sense, Saints should wear a breastplate of righteousness to protect themselves against evil (Isa. 59: 17; Eph. 6: 14). (2) An article of clothing worn by the high priest in the law of Moses (Ex. 28: 13-30; 39: 8-21). It was made of linen and bore twelve precious stones. It is sometimes referred to in connection with the Urim and Thummim (D&C 17: 1; JS-H 1: 35, 42, 52).