Sorry Dean, but I did a google on this (as your wisdom was completely wasted on me), and I hate to tell you (with absolutely no authority) but:
Gneiss is a rock composed of minerals of varying Mohs hardness and therefore would not have a specific Mohs hardness.
Not saying that you ain't hard; maybe just that it is hardness that is immeasurable!!
Here are some with which you can do some more hardness testing right now...
http://five.flash-gear.com/npuz/puz....742&k=65333098
http://five.flash-gear.com/npuz/puz....743&k=28399153
http://five.flash-gear.com/npuz/puz....744&k=68910998