afawcett,
You are really starting to mislead people with some of your statements. Your enthusiasm is great but the facts are wrong.
Go find a driller or a geologist and have a chat about the capabilities of various drilling techniques.
RC is certainly not limited to 'soft rocks' and it depends as much on the size of the rig as the technique used. Factors like the quality of the drill crew, the ground conditions (faulting, groundwater, density of the samples, overburden - especially running sands), and the power of the machine and what air pressure it can run at all play a part. Generally comfortably 200-300m, with some companies saying to 500m, though I imagine in these cases they’d be running a booster and auxiliary to counter the loss of pressure down hole. JE also only has thin cover, likely less than 50m overall and we obviously have the vein swarm at surface.Diamond drilling has its place and will at some point be necessary but it sets up the wrong vision of the project to say it is the 'end goal'. Usually, you end up with a mix of the two techniques. Also RC is sometimes all that is needed for the early campaign, especially on big campaigns where you are mostly interested in grade and interval and not so much focussed on getting precise structural data. The beauty of diamond core is in understanding the structure (satisfies the geo in us all wanting to know every single detail about the puzzle and often required towards the end of PFS etc as you need detail on engineering, metallurgical etc ).
However, pre this latest drilling frenzy across Australia you could get RC for approx $50-100 a metre and diamond would cost approx $250 a metre. I suspect costs are currently higher with the scarcity of rigs. You can see from these cost differentials that if a company is doing a drill out all they maybe interested in is depth intervals and grade to define a resource. The costs are substantially reduced via RC. At Jean Elson, so far, it looks like the potential orebody could be large and though it could easily go deeper than 500m firstly we need to find the top 500m 
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