The singular reference to pearls in the Book of Mormon (other than the Savior's "pearls before swine" reference in 3 Nephi 14:6) is found in 4 Nephi 1:24:
And now, in this two hundred and first year there began to be among them those who were lifted up in pride, such as the wearing of costly apparel, and all manner of fine pearls, and of the fine things of the world.
According to Gregory Witt, archaeological evidence validates the existence of fine pearls among the ancient Mayans. At Palenque, a classic Mayan site, the pyramid tomb of Pacal is adorned with a lustrous sea pearl, displayed in its shell. Similar pearls and pearl jewelry are on display at the Museum of Anthropology in Mexico City and in the Anthropology Museum in Guatemala City.
Nevertheless, early critics of the Book of Mormon claimed that the Book of Mormon reference to pearls was just another evidence of Joseph Smith's folly. One might ask, Why? The answer might be found with the coming of Columbus. Five hundred years ago, oysters were abundant in the coastal areas of Central America and Mexico. Then, Columbus and Balboa arrived and discovered pearls. Most people are unaware that, until the development of gold and silver mines in Mexico and Peru, pearls were the New World's biggest export. In fact, the value of pearls exceeded that of all other exports combined, and in Spain, the Americas became known as "The Lands That Pearls Come From." Over-harvesting of oysters, however, led to a dramatic decline in pearl production (Newman, 1990).
The Book of Mormon reader might also note that the Nephites adorned themselves with "all manner" of fine pearls. Therefore, the question might be asked: Is there any evidence to suggest any notable variety of pearls that would give credibility to the phrase "all manner of pearls"? The answer is, Yes!
First of all, one of the most famous pearls ever found was a pear-shaped pearl about the size of a pigeon's egg. Its owners have been Phillip II of Spain, Mary Tudor of England, Napoleon III, and Elizabeth Taylor. This unusual pear-shaped pearl was not found in the Red Sea nor in Asia, but it came from the Americas.
Secondly, most people are not aware that pearls can be classified as saltwater or freshwater. People are generally familiar only with the round, lustrous salt-water pearls. But freshwater pearls, which are found in mussels or oysters in rivers or lakes, tend to have a more irregular shape. Some almost have the appearance of teeth, small shells, or even Rice Crispies. These lesser known freshwater pearls have also been found in Mesoamerica, and were used as ornamental jewelry by the ancient Maya.
So once again, the Book of Mormon is surprisingly specific in its phraseology. [Gregory Witt, "All Manner of Fine Pearls," in The Book of Mormon Archaeological Digest, Vol. II, Issue I, 1999, p. 15]