"why are you using an 8% and 10% discount rate and not including the standard 5% discount rate for Gold resource?"

Here are some recent reporting discount rate examples for gold deposits; I chose 8% and 10% but you can run the numbers for whatever you want.

1.13gm/t is the grade of the Sept 2007 43-101 Proven and Probable Reserves of 464 million tonnes yielding 16.86 million ounces @ $550 gold. The grade would go down as the gold price goes up and more oz are added to the reserves. I did not adjust the grade downward for my calc at 25.5M oz, so the NPV numbers are based on insufficient mine thruput, but I plan to wait for the SNC update to revisit this.

Regards

kimberresources.com/News.aspx?newsid=181
mexico 8%, 5%
vitgoldcorp.com
nevada 5%, 10%
rollingrockresources.com/s/Home.asp
canada 5%
coralgold.com/s/Home.asp
nevada
8% 11.5% 15%
cassidygold.com/s/Home.asp
africa 10%
rusoro.com
venezuela
8%