How could anyone have believed motormouth when he PROMISED to bring coal mining jobs back?

OK Rosie, I'll explain it.

Coal is not used to fuel modern manufacturing plants, and is used a lot less for domestic heating, but it can be distilled by heating it in a closed vessel called a retort.

That drives off the tar, gas and sulphur compound it contains and leaves coke, which is nearly pure carbon.

Coke used to be used a lot as  aheating fuel because if used in a properly-designed stove, it burns very slowly but gives off a great deal of heat.

Coke's modern, main use is used in smelting iron-ore, i.e. chemically reducing the ore to iron. Iron ore is iron oxide (rust!), and in the fierce heat of a blast-furnace the carbon is not just the fuel, but it reacts with the ore to transfer the oxygen from that to itself, turning the carbon to carbon-dioxide.

Iron is the base material for steel, and is also used as iron, in certain modified forms.

Pure iron has particular magnetic properties that make it ideal for concentrating the magnetic field in electrical generators, transformers and motors.

Cast-iron is iron mixed with graphite (another form of carbon) and it has certain properties making it very useful making some classes of engine and machinery parts.  

Mix iron with a much smaller amount of graphite and you produce steel, and that can be modified further by adding a tough more carbon, or other metals. Add nickel and chromium to the steel and it become stainless-steel.

"Steel" covers a huge range of varieties, including the stainless ones, all developed for certain properties valuable for particular practical applications.  It is a vital material we just cannot do without. It is no exaggeration to say almost everything we use everyday has steel implicated in it somewhere, not always visibly, not always even in the thing anyway; but in its manufacture and transport, etc.

So we still need iron-ore and the coal (from coke) to make new steel, though old steel can be re-melted for new uses.   As far as I know, no-one has found an alternative way to smelt the ore than melting it in an intense, white-hot fire of coke. Certainly not a way that is economical and would not bring problems of its own. It might work by heating the ore in a closed tube and passing hydrogen over it - but you need to produce the heat and the hydrogen, probably both needing vast amounts of electricity.

The furnaces used for re-melting steel and iron can be electric, but also need all that electricity.

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What of the tar and so on from the distilled coal? This can be further processed to extract various useful chemicals, and what is left is just that - tar, useable in road-making. Another by-product is gas that can be used as fuel, and was, on a large scale until the advent of natural-gas in the 1960s.

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Coal-mining... Miners have probably not used canaries for a very long time. They would use proper gas-detectors now, which are portable electronic devices an da lot more accurate than a bird on a cage. And more humane! Coal-mines are heavily ventilated by using two shafts on each side of the seam, and forcing air down one and up the other, but the risk of methane (natural gas) is still there. That is the inflammable one that can form an explosive mixture with air.

Canaries were used to detect high carbon-dioxide or low oxygen levels in the air. The Davey Safety-lamp was used for testing for methane. It is a special paraffin (kerosene) lamp whose flame is enclosed by a strong glass tube below a chimney made of fine steel mesh, which made any methane burn in the lamp flame, turning it from yellow to blue as the indicator, without setting off the methane in the surrounding air.

I have a Davey lamp that used to belong to my uncle, who was a coal-miner in the English Midlands. It's lost the safety-lock that prevented anyone opening it underground, and sadly also lost the colliery name-plate, but it still works. Though I've not tried it in a gassy mine!

The real health hazard to miners is not bad air but the  dust. It coats the lungs and over many years can cause all sorts of unpleasant diseases. A former girl-friend of mine was an ex-miner, and he had emphysema from years of breathing coal-dust in small mines that were probably not very well ventilated. I met him only once, and I could see how bad he was, struggling to breathe even when just sitting in an arm-chair. He had hardly the energy to do much else. 

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Miners could not have been claustrophobic, but would anyway would have become used to the conditions. At one time, they would work seams down to about eighteen inches high, by hand; but as the process became mechanised I believe they extracted only the thicker seams. Some may have lost their nerve after accidents, especially in those old days when the work was very much more dangerous.

Coal is fossil peat, from ancient tropical peat-bogs, so it exists as layers, called "seams", with fossil soil under them and other types of rock on top, but all these rocks are weak. Because it is mined as a layer rather like taking the filling out a sandwich, the roof has to be supported all the way along the narrow strip actually being worked between tunnels cut across the seam. The coal-face is the wall of that strip. Once that face has been cut back by the coal-cutting machine's width, everyone and everything moves forwards, leaving an ever-widening unsupported. void behind, and over time that slowly collapses on itself.

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I mentioned metal-ore mines. Many ores including that of iron, occur in large concentrations at shallow depths so can be extracted by open quarries. Otherwise it occurs as "veins" formed in natural fractures in the rock, rather like the veins of mould in blue cheese. Metal mines are a lot safer than coal-mines, because they do not contain methane.

I have visited a tin-mine in the far South West of England, still open but on a caretaker basis - it closed for a good a few years later. We descended the 1100-feet deep entrance shaft, standing in an enclose cage a bit like a large locker, to the main level, and after walking for some distance, boarded a cable-tram that took us down an inclined shaft to the 1400-foot level, though the shaft continued deeper still. We were actually out under the sea at the point, where we were shown the huge automatic pumps that kept the mine drained.

The mine is now its own museum, and I did visit it. The entire mine itself is flooded nearly to ground-level, probably beyond recovery, but all the buildings and plant are still there. I stood by the grid covering the top of the shaft, and could just see the water below. It was strange remembering I had been down there, and because the whole place had not been over-curated it felt somehow haunted, and certainly very sad.

I asked what the former miners did. Some found non-mining work locally. Others worked for mining or civil-engineering tunnelling companies elsewhere; but their county, Cornwall, is now a very depressed area having lost most of its once-major industry and relying mainly on tourism, farming and the much-reduced fishing.

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Depth? Claustrophobia does not come from the mine's or cave's depth below ground, but the size of its passages. You can't tell if you are deep down below the entrance level unless the route is obviously down-hill, but you can see the roof and might even be able to touch it. Or have to crawl. Or not. I have been in caves so high you cannot see the roof even with a good lamp. I have also been in passages so high and wide I could not see the sides either - and that's a strange feeling!