Idk...maybe just do a dip on as much of the rock as you can, visually inspect...quick scrub of the rock. I just don't think you want to stress the nem too much.
It's difficult to tell clearly but it might be a touch bleached, so when you do add it to the dt, be sure to start low with it and see watch where it decides to "make home".
Looks to be a nice-sized one! Congrats on your new addy!