I am writing about this to warn other hikers about the rock quality around Lake Mead. To put it succinctly, it's sucks. The rock is known to be loose and breaks easily. This is the reason I am not a fan of Lake Mead hikes. All scrambling routes out there need to be done with extreme caution. Deviating even five feet from an establish route can put you on untested rock with dire consequences.
Of course rock can break anywhere, not just Lake Mead. You need to test hand and foot holds before committing to dangerous moves. The two times I have taken a fall were due to handholds breaking. If you do enough scrambling type hikes, eventually a hand or foot hold will break. It just depends on luck if your fall will be inconsequential or not.
It all comes down to reducing your risk. If you stay on established routes, hike in areas with better rock, test your holds, and stay away from dangerous hikers, you will reduce your risk and most likely have many years of fun and safe hiking.