This is a Micro crack in steel as seen through an electron microscope. (Though it appears someone in our household photo-shopped the saved science 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 (yes, Gunsmoke reference for those of us over 50). We're off to Ferrous Canyon! You all be safe out there,I got the internet back up but I lost a day of work, so blogging will be light this evening.
MY favorite Gunsmoke character is Miss Kitty