Different types of corals according to different point of view

From the point of view in appearance, there are four types of corals.
Stony coral is the classic types of coral jewelry. Best known for its distinctive red color, stony coral has been highly prized for hundreds of years as attractive jewelry. Stony coral and pearls share much of the same chemical composition.
Horny coral uses keratin-like proteins. It can be dyed this way through the use of hydrogen peroxide because horny coral creates its home out of proteins similar to hair.
Sponge coral is less compact than stony coral. Thanks to their porous structure, they are rougher in texture and do not polish as well. Sponge coral has a natural blue color that isn't seen often in other types of coral.
Sea bamboo coral is named specifically for its similarity to bamboo. It combines the calcium carbonate structure of stony coral with joints of protein like horny coral. This coral is most prevalent in white with brown or black bands.
From the point of view in hardness, the types of corals can be divided into hard coral and soft coral.
Hard corals are made of rigid calcium carbonate (limestone) and appear very much like rocks.
Soft corals are also composed of some rigid calcium carbonate, but it is blended with protein so it is less rigid than hard corals. These corals are "rooted," but because they have no exoskeletons, they sway back and forth with the currents, appearing to be more like plants blowing in the breeze.