Have any of you worked with crystal or stone skulls? Did you find it different than simply dealing with stones and crystals of the same material?

I have collected 8 or more smaller skulls of different stone (smokey quartz, labradorite, sodalite, sardonyx, tiger iron, mookite, etc) but admittedly don't know how to effectively work with them. If any of you have tips or personal experiences in this area it would be neat to share.