I can certainly say that the Worker's set influences mining results more than the Field equipment. I was lucky to come home after mining with four Darksteel (Gusgen Mines, by the way). Now, with full Worker's gear, I normally return with 6-9 Darksteel. However, as for the Gold, it can vary. I've returned with 1-4. Stocking my Gold away for my devious plans to raise my Goldsmithing when the time comes.
I was thinking about making a statistical proof of its use, but if I tested Field with Worker in my possession, I'd just think of all of the Darksteel I could be getting. ._.;