These are new pumtek beads, and not imitations.

The material they are made from is opalized palm wood. However, the original trees had some gaps or splits in the wood, and there are places where the opal substitute/deposition is "plain" because it has just filled this gap—and does not preserve the grain of the wood. Consequently, it's not unusual for pumtek beads to be made from this material, and to result in beads that do not have a palm-wood grain, or only partially have it.

Lucky you, to get such a large central bead. They are all nice. Can you show the red bead closer?

Jamey