PW,

Reverse Circulation produces 'rock chips' and fines. You log them but mainly you bag them for assay as they come out.

Diamond drills produce core which is logged.

Long holes. Anything beyond 500 meters starts to slow down dramaticlly as pulling core, changing bits, the torque you put on the drill string all negatively influence how long it takes to drill. For the top 400 meters you can expect 70 - 120 meters per day depending on ground condition (hardness, fracturing, variability etc). From there it starts to slow down an drilling gets riskier. Torque the drill string to much and you can shear it off (bad news). Find a big cavity and you can crash the bit, etc etc. By the time you hit 600-700 meters it can take an entire shift to just pull the drill string to change a bit, every 3 meters you have to pull core which takes longer and longer, so drilling slows down to about 40 meters a day or less. Sometimes much less. By 700 meters the drillers are strongly suggesting you shouldn't drill further.

I've seen a few drill holes that are longer than 700 meters but not many. The other thing that people don't talk about is that drill holes are not straight nor do they have that nice gentle curve you see on cross sections companies provide. Long holes snake all over the place (stick ten straws end to end and see how much you can flex them) so you seldom end up on 'target' and they get very expensive per meter. Hence most companies don't drill long holes and opt to investigate the depth of the deposit later when they go under ground with a shaft or decline.

That said I would love to see just one super long hole that stays in the zone through to the end of hole when they finally have to abandon it.