The other instrument, which Joseph Smith discovered in the ground years before he retrieved the gold plates, was a small oval stone, or “seer stone.” As a young man during the 1820s, Joseph Smith, like others in his day, used a seer stone to look for lost objects and buried treasure. As Joseph grew to understand his prophetic calling, he learned that he could use this stone for the higher purpose of translating scripture.

Apparently for convenience, Joseph often translated with the single seer stone rather than the two stones bound together to form the interpreters. These two instruments—the interpreters and the seer stone—were apparently interchangeable and worked in much the same way such that, in the course of time, Joseph Smith and his associates often used the term “Urim and Thummim” to refer to the single stone as well as the interpreters. In ancient times, Israelite priests used the Urim and Thummim to assist in receiving divine communications. Although commentators differ on the nature of the instrument, several ancient sources state that the instrument involved stones that lit up or were divinely illumined. Latter-day Saints later understood the term “Urim and Thummim” to refer exclusively to the interpreters. Joseph Smith and others, however, seem to have understood the term more as a descriptive category of instruments for obtaining divine revelations and less as the name of a specific instrument . . . Most of the accounts speak of Joseph’s use of the Urim and Thummim (either the interpreters or the seer stone), and many accounts refer to his use of a single stone. According to these accounts, Joseph placed either the interpreters or the seer stone in a hat, pressed his face into the hat to block out extraneous light, and read aloud the English words that appeared on the instrument. The process as described brings to mind a passage from the Book of Mormon that speaks of God preparing “a stone, which shall shine forth in darkness unto light" . . . Another scribe, Martin Harris sat across the table from Joseph Smith and wrote down the words Joseph dictated. Harris later related that as Joseph used the seer stone to translate, sentences appeared. Joseph read those sentences aloud, and after penning the words, Harris would say, “Written.” An associate who interviewed Harris recorded him saying that Joseph “possessed a seer stone, by which he was enabled to translate as well as from the Urim and Thummim, and for convenience he then used the seer stone.”