why, page-36

MOU didn't run any sort of geophysical survey to my knowledge. Magnetics is not much use in coal because, of course, coal is not magnetic. About the only thing it's useful for is tracking igneous intrusions that cut through your coal deposit and it can be pretty good for that.

You can do both ground and air magnetic surveys but for a smaller area like this ground would provide a higher resolution.

Better for this sort of coal deposit would probably be a gravity survey. I know of one major coal deposit I've worked on (Wolfang, currently a Rio mine in Qld) that was detected by gravity survey, because the lower mass of coal shows up as a gravity low, even though the coal is buried under 100m of basalt. Pretty amazing stuff. So yeah, it can go quite deep.

But none of these surveys are any good at determining coal quality.

And I suspect that MOU knew about this coal from old boreholes that were drilled years ago. But I don't know for sure.

Re: your previous post... I haven't really been following any other Mongolian coalers since HUN went. So I don't know anything about DRG, but if they've got a 40m soft coking coal deposit that is pretty impressive (as long as it's at a mineable depth).