Black coral is a very precious and rare coral, which is highly sought after by the jewelry market because of its unique appearance and scarcity. It is shaped like a branch, with delicate branches and flexible texture, so it is endowed with the reputation of underwater Shenmu. The growth rate of black coral is extremely slow. It takes 200 years for a sea willow to grow to the height of 1 m, which makes its supply very limited. Due to the favor of buyers in China, black coral is currently sold at a high price in the border areas of China. In the international market, the price of a black coral ring inlaid with gold is usually between 1200- 1500 dollars. These factors lead to the high value of black coral.