Thank you for submitting your item for appraisal. This appears to be a piece of limestone or concrete. The human brain tries to make sense of what the eyes see. Due to that computing effort some may see things in the clouds or other chaotic structures which are not there. So what you see in that stone may only be visible to you and no one else. It is just how the human brain works. The stone in your possession is an interesting conversation piece, but there is no value to it. There is no measurement for the sentimental value you might attach to it.