I have always been interested in these beads either made with a core or just plain.
We display quite a few examples of them in both states in our Museum.
The ones with a white or yellow core definitely look more like carnelian but the other are sparsely found.
In the picture the two inner stands are just plain glass and the other have a white or yellow core.
The thickness of the red layer do change the aspect of the bead.

JP