"Has brother Brigham got the Urim and Thummim? Yes, he has got everything; everything that is necessary..."

[kirtland r.m.]

The above quote is from Heber C. Kimball. He said it publicly as recorded in the Journal of Discourses Vol. 2. You will find it, and much more really valuable information here.https://www.worksofjoseph.com/urim-thummim/
A few more quotes on this awesome gift.
Joseph Smith

[T]here were two stones in silver bows—and these stones, fastened to a breastplate, constituted what is called the Urim and Thummim ... and the possession and use of these stones were what constituted “seers” in ancient or former times. (Joseph Smith-History 1:35)

Joseph Knight

After breakfast [on the day he received the plates and the urim and thummim] Joseph [Smith] called me into the other room and he set his foot on the bed and leaned his head on his hand and says,... "It is ten times better then I expected." Then he went on to tell the length and width and thickness of the plates, and said he, "they appear to be gold." But he seemed to think more of the glasses or the urim and thummim than he did of the plates, for, says he, "I can see anything; they are marvelous." ("Joseph Knight's Recollection of Early Mormon History," BYU Studies, Vol. 17, No. 1; spelling modernized; online version)

Martin Harris

The two stones set in a bow of silver were about two inches in diameter, perfectly round, and about five-eighths of an inch thick at the centre; but not so thick at the edges where they came into the bow. They were joined by a round bar of silver, about three-eighths of an inch in diameter, and about four inches long, which, with the two stones, would make eight inches. The stones were white, like polished marble, with a few gray streaks. I never dared to look into them by placing them in the hat, because Moses said that "no man could see God and live," and we could see anything we wished by looking into them; and I could not keep the desire to see God out of my mind. And beside, we had a command to let no man look into them, except by the command of God, lest he should "look aught and perish." (Martin Harris' 1859 Interview with Joel Tiffany on Early Events in Mormonism; see online version)

Lucy Mack Smith

I trembled so much with fear lest all might be lost again by some small failure in keeping the commandments, that I was under the necessity of leaving the room to conceal my feelings. Joseph saw this and followed me. "Mother," said he. "Do not be uneasy. All is right. See here," said he, "I have got the key."

I knew not what he meant, but took the article in my hands and, examining it with no covering but a silk handkerchief, found that it consisted of two smooth three-cornered diamonds set in glass, and the glasses were set in silver bows connected with each other in much the same way that old-fashioned spectacles are made. He took them again and left me, but did not tell me anything of the record....

That of which I spoke, which Joseph termed a key, was indeed nothing more nor less than a Urim and Thummim by which the angel manifested those things to him that were shown him in vision; by which also he could at any time ascertain the approach of danger, either to himself or the record, and for this cause he kept these things constantly about his person. (History of Joseph Smith, Revised and Enhanced, p. 139, 145)

I have seen and felt ... the Urim and Thummim. They resemble two large bright diamonds set in a bow like a pair of spectacles. My son puts these over his eyes when he reads unknown languages, and they enable him to interpret them in English. (in Henry Caswall, The City of the Mormons; or, Three Days at Nauvoo, in 1842, 2nd ed. revised and enlarged, (London: J. G. F. & J. Rivington, 1843), 26)

[stillwater]

It's worth noting that Joseph Smith's various seerstones were also referred to as Urim and Thummim. The Church has been in possession of a few of these, and Heber was probably referring to one or more of those stones. There is no record that I've ever seen of the Jaredite seerstones (set in the silver bow mounted on a breastplate), after they were shown to the witnesses of the Book of Mormon.

[kirtland r.m.]

It's worth noting that Joseph Smith's various seerstones were also referred to as Urim and Thummim. The Church has been in possession of a few of these, and Heber was probably referring to one or more of those stones. There is no record that I've ever seen of the Jaredite seerstones (set in the silver bow mounted on a breastplate), after they were shown to the witnesses of the Book of Mormon.

“I have Joseph[’]s 1st Seer Stone which I [h]ad from O[liver] C[owdery],” President Young acknowledged in 1853. There were others as well. “Joseph [h]ad 3 which Emma has,” he added, “2 small ones and 1 large one.”29 Two years later, Brigham Young told a group of assembled Church leaders that “Oliver sent me Joseph’s first Seer stone, Oliver always kept it until he sent it to me.”30

After Brigham Young died, one of his wives, Zina D. H. Young, who later became the third Relief Society general president, obtained a chocolate-colored seer stone from his estate that matched descriptions of the stone Joseph used to translate the Book of Mormon, and donated it to the Church.31 Since that time, subsequent Church leaders have acknowledged the Church’s ownership of the seer stone.32https://www.churchofjesuschrist.org/stu ... r?lang=eng