Zhen Zhu Mu

Zhen Zhu Mu, mother-of-pearl, is the iridescent inner nacreous layer of the shells of pearl-bearing marine and freshwater bivalves, principally the marine winged pearl-oysters Pteria martensii (now Pinctada fucata martensii) and the freshwater mussels Hyriopsis cumingii and Cristaria plicata (Bivalvia, Pteriidae and Unionidae). The nacre consists of microscopic platelets of aragonite (calcium carbonate) bonded by an organic conchiolin matrix, producing the characteristic structural iridescence. The shells are harvested from cultured or wild beds, the dark prismatic outer layer is scraped or ground away to expose the smooth pearly inner surface, and the cleaned material is crushed, calcined, and ground to a fine powder, often by water-levigation. In traditional Chinese medicine the prepared substance is sweet, salty, and cold, anchoring the spirit and pacifying the Liver for palpitations, insomnia, irritability, dizziness, and headache from Liver-yang rising, and clearing the eyes for red, swollen, or blurred vision.