Twelve Stones for Twelve Tribes, Four Rows of Three

The hoshen, usually translated as breastplate or breastpiece of judgment, was a square panel of fine linen worn by the High Priest of ancient Israel over the ephod, set with twelve engraved gemstones arranged in four rows of three, one stone for each of the twelve tribes of Israel, so the High Priest bore the people's names over his heart in service just as the ephod's shoulder stones bore them on his shoulders. Exodus names the specific stones in order, though the precise identification of several ancient stone names with modern gemological categories is uncertain, since stone terminology has shifted considerably across three thousand years of translation and trade.

The breastplate was folded to form a pouch, doubled rather than a flat panel, and it was this pouch that held the Urim and Thummim, the objects used for priestly oracular inquiry, which is why the garment carries the epithet of judgment: it was the instrument through which the High Priest sought a divine ruling on matters brought to him. Which specific stones the Hebrew names refer to is debated among translators, since several of the twelve terms have no certain equivalent in modern gemological vocabulary, so translations into English and other languages vary from one Bible edition to the next.