Raw crystals are as they come from the ground and due to this reason, they may still contain clay residue.
We try our best to dust this off whilst handling the stones as little as possible, as the majority of crystals absorb energy. Although we cleanse all of our crystals before they are rehoused, we want to alter the natural energy as little as possible.
If you find that your stone has quite a lot of clay residue, you are able to remove this by gently dusting off the residue with a bristle brush.