Onyx Cave located 31 43 50 N 110 46 183 W From Tucson go E. on 10 Turn S. on 83 (Sonoita Hwy) Then go W. on Gardner Canyon Rd. Then take FR 4085 stop at bottom of the Mt. take trail to the top of the Mt. Yes it is located on top of the Mt. It is also gated by a local Grotto. Very close to Cave of the Bells 31 43 700 N 110 46 67 W. 2 other caves in the area too, Agua Caliente Cave 31 41 15 N 110 57 31 W & Silver Cave 31 37 30 110 47 33. Have fun be safe Drdanieldavid@hotmail.com