Is this a rock with metal or gold?
If it's really hard, I'd tend toward an iron base mineral of some kind. Gold is not very hard. Just hedging bets, you should always bet iron because its so common. 

It also doesn't look like any gold ore I've ever seen, but I've only ever seen pictures. I understand that gold ore usually has free and unattached veins (looks like lovely yellow gold stuck in a rock), while the small remaining minority is wrapped up in pyrite or something else by as much as 1 oz gold to 1 ton rock (not very profitable outside of industrial mining). Unless there's literal tons of it, I'd just carry on with your business. 

I'm not sure what lab testing would cost or even how available such services are, but if you can find something cheap enough and they also promise anonymity (you want privacy if you're sitting on a literal gold mine), might be worth quelling the curiosity.

A quick google search found this site: How to Test for Gold Ore - Sciencing. The page promises to be an accurate, at-home testing method for identifying gold ore. You would need some acids (I guess you can just buy those) and gold testing wires (which might be expensive).