Here's a quote from Ales Hrdlicka's report on "Lansing Man" -- a skeleton found near Lansing, Kansas in 1902, which was proposed as extremely early evidence of humans in the New World. Hrdlicka made it his business to examine such finds with a critical eye, he was the first physical anthropologist to espouse the theory that New World peoples reached the Americas by the Bering Strait route relatively recently.
The bones are quite hard and not very brittle; they are not sufficiently chalky to mark a blackboard. They fully preserve their structure and exhibit no visible traces of fossilization.
This just has me giggling. The thing is, I know exactly what he's talking about -- I've studied many skeletal remains where they would be chalky enough to mark a blackboard.