The coral you find in jewelry really isn’t. It is a calcium carbonate skeleton that is produced by coral polyps that live in clean, rich tropical and subtropical oceans.
Coral has been used for jewelry back some 25-30,000 years. Many people around the Mediterranean, where most of the deep red coral was originally found, used it for jewelry. The Egyptians and Romans place high value on it.
Native Americans have used coral in jewelry since about 600 years ago when the Spanish showed up with it as a trade item.
Even then, its use in Native jewelry was not common because of its high value. The Zuni, Santo Domingo, Hopi and Navajo drilled holes in pieces of coral, strung them, along with turquoise and shell on bark string and created bead necklaces. This style of jewelry is still popular among Native tribes of the Southwest. Many people collect and wear these “heishi” necklaces.When the Navajo and Zuni began making silver jewelry, they incorporated coral, along with turquoise and shell, in their work. Still, it was rare because of cost.
In the 1960s and 70s it was not uncommon to see coral cabochons combined with turquoise and silver in Navajo jewelry and for the Zuni to use small pieces of coral for inlay and needlepoint work. But the material was, and remains, very expensive.
There was a man who ran a company called M and M Indian Jewelry back in the 1970’s who showed at different wholesale markets. He made a career of selling coral and turquoise silver jewelry and his booth was always packed with hundreds of pieces of this jewelry. Because of over harvesting, coral is more rare and expensive today. I doubt anyone could put together a collection like he had just for lack of material.