[From the Wikipedia article:] To scientists, one of the more fascinating findings to emerge from this well is that no transition from granite to basalt was found at the depth of about 7 km (4.3 mi), where the velocity of seismic waves has a discontinuity. Instead the change in the seismic wave velocity is caused by a metamorphic transition in the granite rock. In addition, the rock at that depth had been thoroughly fractured and was saturated with water, which was surprising. This water, unlike surface water, must have come from deep-crust minerals and had been unable to reach the surface because of a layer of impermeable rock.
Another unexpected discovery was a large quantity of hydrogen gas. The mud that flowed out of the hole was described as "boiling" with hydrogen.
> Did they find any precious metals, etc.?
These concentrate in veins, so the single borehole would not be the best way to find out. They were probably recorded in mud logs somewhere.
> is it possible to measure the depth of the hole using a laser
Holes like this are very rarely totally straight as the geology likes to manipulate the drill string as it descends. Whilst this won't be a true deviated well (due to the research goals) I'd be very surprised if there's a vertical hole.