Glad that helped you out.
The main mine I'm working with has a core drill (old Boyles Brothers pneumatic) but nobody who knows how to use it, myself included. Having it contracted will be very expensive - drilling contractors usually charge by the foot as well as a substantial mobilization fee. You could certainly use a "backpack" or other small core drill, and will probably be decently happy with its work product as far as getting you core in hand, but core is not foolproof and can give misleading results in a pockety deposit.
The mine down here is gold/silver hosted in a portion of a quartz vein. Especially in the upper levels, values are primarily contained in "black sulfide" (pyrrhotite) nodules with irregular size and spacing. They're typically marble- to baseball-sized and can run $50,000 per ton but the overall ore averages 0.15-1opt Au because of the barren quartz.This makes for a sort of reversed nugget effect, where a single core hole can hit barren quartz and miss a super-high-grade nodule by less than an inch. Short-range exploration has therefore taken two forms: drifting (more feasible with a 911, other small loader, or a slusher) and longhole drilling.
The latter would be my suggestion to you - an air track drill or heavy jackleg with steels capable of being threaded together can drill surprisingly far. You'll get cuttings rather than cores, which is less visually impressive but cores have to be crushed for assay anyways...only practical downside is the comparatively limited drill distance and the fact that your intervals will not be as cleanly defined.
We've discussed 50' production holes with the air track, which we believe is about the limit before downhole deviation becomes enough to cause problems in a longhole stope (overbreak/underbreak/dilution). The particular drill in question is a Gardner Denver 3100 with a PR-123 hammer and upgraded hydraulic centralizer. You can go further but the hole will start to wander a bit - just remember that the requirements for production blasting are different for those from short-range exploration. Obviously a jackleg will not drill as far - the hammer just isn't as strong. I can ask about what practical distances they've achieved with Gardner Denver 83s versus one of the about five air tracks scattered across the district. While the crew did do something like a 200' longhole to assess a high-pressure injection dewatering technique before a discharge permit was greenlit, these drills suffer exponential decay in drilling speed with very long holes.
Just remember that whatever equipment you buy, you're buying into its dealer/parts ecosystem as well. While EIMCO got gobbled up by Sandvik, only the axles and drivetrain components are especially uncommon - a good shop can rebuild much of that. The engines, tires, and hydraulics are commodities that most tractor dealers will support, and Pillar Manufacturing is happy to sell miscellaneous spares. Same for Young Buggies - they're a Deutz tractor engine, Funk 33000-type HMD transmission and reverser, an Eaton rear end, basic hydraulics, and a bunch of sheet metal work. Bobcat will be even better.
