Should Akadama do this?
 

Hello. I recently bought some Akadama from a website (dallasbonsai or
something) about a week ago. The actual akadama particles seem to be
lava rocks surrounded by clay material. Since I have been watering the
soil, I notice that the clay on some of them has been washed away, leaving
just the core of the soil behind, which doesn't hold moister as long.

So the thin clay layer surrounding the lava rock is being washed away by
watering, leaving the exposed core. Is this normal?

Brian