This is a Micro crack in steel as seen through an electron microscope. (Though it appears Partner in Grime photo shopped the saved photo.) I've vacationed at places that looked like this!
Of course the folks on NCIS wouldn't need an electron microscope. Gibbs would just squint and go "ahh yup - micro-crack", before Abby could even consider micro-cracks at the surface of metals detected and imaged by near-field microwave techniques from the crack-induced variations of the resonance frequency and of the resonant circuit quality factor. I mean really, you have to get this thing solved in an hour WITH commercials.
Fire up the welder Festus, we're off to Ferrous Canyon! You all be safe out there, I headed back to Indy a day early to beat the winter storm barreling down from Canada so I'm not late for work.