Sandpearl
an opaline stone found in the last chamber of a krayt dragon's gizzard, these stones are also called dragon pearls. The krayt dragon ingests stones of various sizes and materials for use in its gizzard to crush food for easy digestion. When the stones get too small, they are expelled. The resulting pearls have been smoothed and polished to a brilliant finish, and have various values depending on their color and size.