I found this in my garden when I was digging out an invasive weed.  I was keeping some interesting stones in a separate pile to add to stone edging I have around a garden bed.  I saw it, and even covered in soil, it looked interesting.  I removed some dirt and saw it was really lovely.  At first I thought it would be porcelain.   After I removed more dirt I realized that it isn’t.  Both sides are truly beautiful.  It looks like a mushroom to me - the detail is amazing!  I don’t know anything abo