We are told here in China that the rough material comes from Indonesia, specifically from Bali. I have not, however, seen the rough in Bali.

The dyed red material sold in the Philippines might be a limestone held together with plastic resin. It used to be called tiger coral in beige/white and now dyed red. The outside is shiny with some black/grey trailings to look like a natural stone but the inside is crumbly and white.

Most of the red sponge coral used in Bali and China in jewelry is man made block material. Some beads are still made from the natural and dyed sponge coral.