Other interpreters suggest that the Urim and Thummim were separate objects that were both kept in a pouch on the breastplate. In the Bible we read about one individual who made a counterfeit breastplate for his personal cult. For his breastplate he substituted teraphim for the Urim and Thummim (Judges 17-18; Hos. 3:4). This is a tantalizing but frustrating bit of data, because we know even less about the teraphim then we do about the Urim and Thummim. Consequently, the association of the two objects does not shed much light on either, no pun intended. The best evidence is that the two may have both been made of light-reflecting stone; Mesopotamian sources also mention an elmeshu stone used by the gods for oracular purposes.
The context for its mention in Scripture indicates the Urim and Thummim was only used for questions of grave importance, usually connected to the function of the state, such as whether and when to go to war, though there is one passage in Numbers that hints at the possibility it was used for more mundane questions, such as resolving difficult legal questions. The answers given by the Urim and Thummim recorded in the Bible were full sentences, suggesting either that the device was merely an aid to oracular prophecy, or that the Rabbis were correct in their claim that it spelled out messages from the letters on the breastplate.
Mention of the Urim and Thummim ceases early in the history of Israel, indicating that it was no longer in use at the rise of classical prophecy (8th Century BCE). There is some indication that it was reintroduced briefly during the Persian period, but it quickly disappears from the records. Since then it has become part and parcel of Western occult lore; Joseph Smith claimed to have used the Urim and Thummim to read the "Reformed Egyptian" language of the golden book given him by the angel Moroni. (DDS 4QQ376, 4QpIsa; Antiquities; B. Yoma; Exodus Rabbah; Number Rabbah; Sifrei Numbers; Targum Pesudo-Jonathan; PdRE; Zohar; Ramban on Ex. 28).