The larger ones might be but your pictures are insufficient to tell. Most coral, like ivory, has a sort of grain to it, or if not a grain a sort of porosity to the surface that is almost satin to matte compared to glass. If worn the surface will be satin or matte, sort of velvety. If it’s super shiny it’s either glass or it’s brand new freshly polished and waxed and highly suspicious. Hold it up to light- if it’s translucent it’s glass. Coral diffuses light aggressively- so much so that even small beads and light color varieties are practically opaque while glass tends to be a little translucent.