The obvious answer to your question would be the geologist...

The obvious answer to your question would be the geologist logging the core picking up some tiny flecks of visible gold, however not likely on first hole unless you've drilled right into the guts of a deposit or high grade shoot (we'll need to wait for assays for the gold grades). Alteration of the host rocks will be the most obvious indication of potential to host mineralisation after that... most often with gold mineralisation you get pretty obvious alteration that tells you there's been a lot of hot fluids through the rock. The other thing that we are likely to see in the core here is substantial quartz veining (as well as the type of quartz veining). However, just because we have alteration and quartz veining doesn't mean we'll get gold (unless you can see the gold obviously). But seeing intense alteration with a lot of quartz veining as well as shearing/structures will be very encouraging. The real valuable visual information that can be extracted from the 1st diamond hole will be to work out lithology and structure, this will help "orientate" the company and ensure future drilling is optimum, in large part because they are currently drilling "blindly" and going off the geophysics. Hope that answers your question