When you wack it, make sure you are wearing gloves & safety glasses.
After rockhounding for years; I took a wack at a big limb casting of petrified (really hard silicified) wood which had a rind on the outside; in order to see what it looked like underneath...
I was wearing safety glasses but hadn't taken the trouble to go put my gloves on, as I was busy sorting pieces of material out of a 4'x4' tote & would have had to walk 15' to where my gloves were sitting.
The rind fractured & I thought a chip had bounced off my right forefinger, as it bled like crazy.
There was actually a small chip of the rind which had penetrated all the way to the bone in the finger, on the left side & just below the knuckle... which I had to have removed about 3 years later due to chronic pain.
It showed up on an MRI, & the surgery wasn't cheap...Safety is important. You can lose your eye if your not careful.