There are miles and miles and miles of walls (and roofs and floors) in old mines. 99.9 % + of them are of no merit.
Perhaps you would care to enlighten us as to criteria by which you personally judge the passages to be of no merit. Whilst you're at it, you could also justify why "In that situation the minerals surely have priority". For study purposes, there are plenty of damn good specimens already above ground, why does any mineral exposure have to become fair game for removal by anyone who claims an interest in it? I also don't agree that you cannot appreciate minerals underground - I have an interest in minerals but I can enjoy a good example of veinstuff where it is without feeling the need to bring it to day.
"look at mine tips". Yes look at them - while they last. As part of its Lead Rakes Project in the Peak District, English Heritage produced a report (Bulletin 42) on the state of the mine tips, or "hillocks" as they called them, in the Peak District.
One of the two authors, John Barnatt, is registered on AN and I've emailed him to draw his attention to this thread, as I suspect he may have some comments to make about his work being used to justify mineral collecting. I will however point out that a) the bulk of hillocks in the Peak were generated by miners surface-trenching to expose and assess the vein, rather than as a result of mining and b) what mineral is in them is not specimen quality, hence why they aren't much disturbed by collectors. If we had a location where they contained something like the Mimetite you get from the Caldbeck mines, I expect the situation would be very different.....
Only to those with a gripe against collectors is it "ransacking". If the mines collapsed irrecoverably tomorrow then "rescuing" might be a better adjective. As I understand it, many of those who have dug out large sections of these mines have been collectors, and their actions have made areas accessible to all including significant historic remains.
There is an assumption behind the argument that digging by collectors is a good thing because at Nenthead it opened up new ground, which is that no-one else would have done it if they hadn't. There are several AN members who will testify that this is not the case, and these passages would have been dug out in due course anyway.
"not as the miners left it" The miners themselves did not always leave things nice and tidy. Pillar removal at the end of a mine's life has, doubtless, left many a mine sealed forever. With respect to specimens, I once found a piece wrapped in ancient newspaper (early 20th century) by a miner, and elsewhere in the same mine (Rampgill) vugs scraped clean by the miners themselves (their own rusting tools and rotten newspaper giving it away) presumably to get material for their spar boxes.
It was the job of the miners to remove minerals, and the condition that they left the mines in is irrelevant to this argument. The critical factor is how those of us who go into them treat them, and the general consensus is that we should be aiming to leave nothing but footprints and take nothing but photographs. This thread was started to discuss the NAMHO guidelines on artefact removal, which try to set out the limited circumstances under which we should consider departing from the ideal.
So let's put this into perspective please. The main threats to mine sites do not include collectors, and without collectors the minerals would be lost anyway when the mine falls in or the farmer removes the tip. Mines are not the exclusive preserve or one group or another. There has to be a bit of compromise on both sides. Yes leave the historic stuff and structures alone, but where these are not affected then leave the collectors alone too.
Whilst I agree that mineral collectors may not generally be a major threat to above-ground remains, on any underground site with something of interest, it's a very different story. Ian Tyler had a rant to me one time when I was in his museum about the damage done to Carrock mine by collectors in search of Scheelite and Wolframite samples, and I could also cite the pulling down of packwall in the back workings at Masson (a geological SSSI...) to get at Fluorite and Calcite.
There is also one major issue entirely avoided here which is
ownership. To go into any mine or quarry and remove something without the owner's permission is theft in the eyes of the law, and to hammer it out or damage anything to get at it counts as vandalism and/or criminal damage. Unauthorised collection is likely to upset landowners, resulting in loss of access for everyone. Add to that the element of collection for personal profit and the tendency of mine explorers to look askance at mineral collectors is understandable.
What this really boils down to is responsibility and respect, for the mines themselves, the rights of the owners, and for others visiting. I would say that anyone who does not respect the places they visit and acts without any thought of the possible implications of their actions has no business being there (catch me on a bad day and I'd say they need dropping down a deep shaft!). Yes, compromises can be reached as can be seen from the links that have been established between archaeologists and metal detectorists but it takes understanding on both sides, and your opening comments about 99.9% of passages show little understanding of the perspective of the mine explorer and historian....
Follow the horses, Johnny my laddie, follow the horses canny lad-oh!