Beauty is of course as they say "In The Eye of the Beholder". Do note that I added "Personally" I have never seen a cyanide job that to me was as attractive as the bone charcoal colors.
As to hardness, note also I did not say the bone colored jobs were harder than the Cyanide, what I said was they normally have a deeper depth of case. The term "Case Hardening" comes from the fact one puts a hard shell/case around a soft core. According to Machinery's Handbook most cyanide hardened parts receive a depth of case of as I recall of .001"-.003" while pack hardened parts can be much deeper than this. In either case the depth of the Color is microscopic being only on the surface. The color being worn away is no indication at all that the hardness of the case is gone, its still right there doing its job.
