Reynolds and Sjodahl have written the following concerning the two stones given to the brother of Jared by the Lord:
These Two Stones, which are also known as the Interpreters (Ether 4:5; Mosiah 28:20) and Urim and Thummim (Pearl of Great Price, Joseph Smith 2:52; Doctrine and Covenants 17:1) were, as we read here, entrusted into the care of Moriancumer, before he descended from the ever memorable scene of his vision and revelations. They were delivered to him with the admonition that they were to be sealed up, together with the sacred records that were to be kept, and thus be hidden from the eyes of the world, until they, in the due time of the Lord, were to come forth. The purpose of the Stones is stated to be to magnify, that is to say, to make clear “the things which ye shall write.”According to the Doctrine and Covenants (17:1), the Sacred Instruments deposited in the Hill Cumorah and delivered to the Prophet Joseph, [were] the Urim and Thummim received by the Brother of Jared on the Mount. When the Prophet Joseph received the Stones, September 22, 1827, they were framed in silver bows and fastened to a breastplate (Pearl of Great Price, Joseph Smith 2:35). From the Doctrine and Covenants, 130:8-9, where God is said to dwell on a globe which is a Urim and Thummim, and that the Earth is to be sanctified and made immortal—made like unto a crystal and will be a Urim and Thummim to the inhabitants thereon—we conclude that that was the nature of the Stones. They were crystals. The Prophet Joseph Smith further adds to our information that the white stone mentioned in the Revelation 2:17, will become a Urim and Thummim to each who receives one, and that a white stone will be given to everyone who is privileged to come into the Celestial Kingdom. On the stone a new name is written. By this means things pertaining to a higher order of kingdoms, even all kingdoms, will be made known. (Commentary on the Book of Mormon, 6:87.)