Besides the artifacts mentioned above, mortars, spindle whorls, pestles and polished pumice stones were unearthed. Two are nude workers, kneeling with pestles and mortars. Large mortars and pestles are commonly used in developing countries to husk and dehull grain. Granite mortars and pestles are used in Southeast Asia, as well as Pakistan and India. Glass mortars and pestles are fragile, but stain-resistant and suitable for use with liquids. Mortars and pestles were manufactured on San Miguel Island for trade with the mainland. Stone artifacts included atlatl weights, gorgets, and pestles. The content of the sculptures fit into three categories&colon; mortars, pestles, and freestanding figures. Folk instruments include pestles, five-stringed zithers and the jaw harp. In the Philippines, mortar and pestles are specifically associated with de-husking rice. Later pestles and a simple machine called a rice pounder were developed to remove hulls. The tops of many pestles contain images, often of birds or human heads. Native implements (arrowheads, pestles, etc.) have been found along the nearby Arrow Lakes.