Beginning with verse 20 we are introduced to another sensational development in Book of Mormon history. It turns out that prior to the arrival of Mosiah and his band of Nephites, the people of Zarahemla had discovered that there was a vast civilization north of their own country. The last survivor of this civilization to the north had wandered down into Zarahemla and lived among them for nine months and then died. His name was Coriantumr.
This man, of course, was the last survivor of the great Jaredite civilization which had come to America around 2200 B.C., and had finally been wiped out by civil war. Before the last survivor, Coriantumr, had run into the people of Zarahemla, he had apparently given up hope of finding any of his people alive and so he had written his biography on a large stone. Afterwards he wandered down south, ran into the people of Zarahemla, and lived among them until he died nine months later.
Eventually the people of Zarahemla discovered Coriantumr's stone. But he had not lived among them long enough to learn his language, therefore they could not read the stone. When Mosiah and the Nephites arrived, the people of Zarahemla hoped Mosiah could somehow read this stone and unravel the mystery of Coriantumr and his people. They were not disappointed. Mosiah read the stone because he had the ability to do so through the Urim and Thummim which had just come into his possession just recently. These interpreters had previously belonged to the Jaredite prophets.4 Illustrations of these latest events are pictured in volume two of Treasures from the Book of Mormon on pages 14 and 15.