So my grandpa passed away he was a huge rock and mineral guy and he purchased this in 1999 in auction and I dont know what it is or where to get it appraised or where to sell it. Its huge its like 30in wide by 14in tall.
It looks to be a large specimen of a 'desert rose'. These are natural concretions of sand, usually cemented with gypsum or baryte, forming bladed or flower-like forms.
Yours is unusually large and would likely be desirable to a collector. I would think it might fetch several hundred dollars in the right auction, but the negative for a prospective purchaser is that you don't have a find location.
All Garrett: Ace 250 (two), AceApex, VX-9. Have owned just about every Garrett ever made. First three detecter I made myself, with the first one in 1962.
Funny this should show up on TreasureNet. A couple of days ago, while watching a YouTube vid, in the foreground were several Desert Rose formations, a few of which were trod upon. Too bad the presenter didn't know what they were worth to collectors.