Naturally occurring Sponge Coral is porous and very rough, with spongy-looking pockets. It is not a sponge, but a type of coral imported from Asia that has a sponge-like appearance. Jewelry quality Sponge Coral beads are stabilized and highly polished, which have had the pockets filled with a polymer or a resin. Quality Sponge Coral has a vibrant orange-red color, some with streaks or tinges of yellow in it; lower-quality specimens having a brownish tint or larger areas of yellow. While the lower-quality specimens are less valuable, they do have a varied visual appearance that can still be valuable in jewelry. Sponge Coral also comes in blue with a gray tinge.