Urim is a white circular stone that says yes and Thummim is a black circular stone that says no

The first prophet of the Church of Jesus Christ of Latter-day Saints (the "Mormon" church), Joseph Smith, claimed that he used the Urim and Thummim to translate the Book of Mormon into English. After the translation was complete, the Urim and Thummim were returned to God.

Nobody else in the Church has claimed to have seen or used the Urim and Thummim.

Urim and Thummim are two gems, one white and one black, that helps Santiago make yes or no decisions.

Technically, the Urim and Thummim are two stones, most often mentioned in connection with a metal breastplate. The stones are often thought to be clear or white and the breastplate silver or gold in color, but the Old Testament never clarifies the colors of these items. Some also believe that each of the stones was a different color, because the Urim was used to determine guilt and the Thummim to determine innocence.

In the LDS movement, Joseph Smith described the Urim and Thummim as being triangular in shape and clear like diamond or crystal.

They provided a form of prophetic answer to urgent communal questions (see Numbers 27:21). An example of this is in 1 Samuel 23:2.