Mu Li

Mu Li is not a plant but the dried shell of oysters in the genus Ostrea, principally Ostrea gigas (Crassostrea gigas), O. talienwhanensis, and O. rivularis, harvested along the coasts of China. These bivalve mollusks produce thick, hard, irregularly oval to elongated shells composed of layered calcium carbonate, typically eight to thirty centimeters across, with a deeply concave lower valve and a flatter upper valve. The exterior is rough, scaly, and irregularly laminated, often encrusted with marine growths, ranging in color from greyish-white to purple-brown. The interior is smooth, pearlescent, and porcelain-white, sometimes with a darker muscle scar. After collection the shells are washed clean of soft tissue, sun-dried, and broken or calcined for medicinal preparation; the substance consists almost entirely of calcium carbonate with trace minerals.