The firm is developing the business and has a trading outfit based in Dubia and exploration licences in Australia.
Wishbone can draw on the facility in multiples of US$100,000 at any time up to June 6, 2018 and it can be repaid at any time.
The interest is 2% per year and 0.5% is payable on each trade of precious metals where the facility is utilised either to support a letter of credit or in direct trading.
Wishbone's chairman and chief Richard Poulden said: "I believe this is an excellent deal for Wishbone.
"Sanderson have recognised the lower risk opportunity of the project with a low interest rate and other fees linked entirely to the success of our operations. Thus far we have traded gold in small volumes constrained by working capital and this enables us to move on the larger contracts, which we have in place. We will issue a trading update as soon as we are able to do so."
Wishbone will pay a 10% commitment fee for the deal. Shares will be issued at 0.54 pence - the closing mid-market price on Friday (June 3).