Black Cyn is just a few miles north from Black Cyn city on 17. I think this must be the place as it is famous in AZ history for the many stage robberies there.
Black Cyn hill, (from AZ place names);
"On the old stage road, Prescott to Phoenix, about 35 miles east of Prescott. The actual Black Cyn was about 10 miles long and was on Bumble Bee. At Gilette it opened out onto the flat country near the junction of New River & Agua Fria. 'Black Cyn Hill' was a one way grade. Drivers waited for each other at certain turnouts, they blew their horn as a warning of their coming."
Let us know if you find gold.
"The good things a person needs-stubbornness, thinking for himself-don't make him a useful member of society. What makes him useful is to be half dead." Sylvan Hart