There are four types of precious coral in Hawaii: black coral (Antipathidae), gold coral (Parazoanthidae), red or pink coral (Corallidae) and bamboo coral. Each of these has a different internal composition. Red and pink corals produce a calcite skeleton similar in hardness to ivory and pearls. Bamboo corals, on the other hand, produce a skeleton composed partially of calcite and partially of protein that is similar to the keratin in your fingernails. These alternating bands of material resemble a bamboo stalk; thus the corals' name. In Hawaii, black corals are found in 100-300 ft. of water, shallow enough to harvest using scuba equipment. Many harvesters, however, have died in pursuit of coral trees at the deep end of this range. Red, gold and bamboo coral are found between 1,000 and 1,500 ft; so harvesting is conducted with remotely operated vehicles (ROVs) or submarines.