I have mapped areas of Bodmin Moor especially around Minions which was originally a mining settlement. Large parts have been mined until around 1900, but it is likely that there has been mining since prehistory.

Early mining, as least medieval, was largely based on streamwork. This is described here (https://historicengland.org.uk/listing/the-list/list-entry/1020051). That describes a particularly large example near Minions. This website (https://www.aditnow.co.uk/Photo/Gonamena-Tin-Streamwork_50013/) includes some photographs.

As seen in those pictures, the ground is heavily disturbed. That case is fairly extreme. Often the area is smaller, but usually following a stream, and only a few metres deep. Frequently the ground is sandy with fine gravel, presumably from the extracted waste. Actually that is true in places at Gonamena, and it is also true of other smaller workings around Minions.

We don’t (yet) have any good tagging for these places, but I had used landuse=surface_mining which I think captures these distinctive areas quite well. Together with disused=yes. Unfortunately another mapper decide to change that tagging to landuse=quarry which is just plain wrong.

I have now changed to historic=mine (I am not keen on that) and landuse=disturbed (also not really a landuse) until someone comes up with better ways of capturing these special places. Perhaps I might change historic from mine to surface_mining.

There is a thread on talk-gb@openstreetmap.org about this.

For the record, I think basic mapping is more or less complete now for:
Curbridge, Ducklington, North Leigh, Wilcote, Ramsden, Hailey, East End,
New Yatt, High Cogges, most of Crawley and Poffley End as well as Minster Lovell.

A few paths are left around South Leigh. The area south of Ducklington needs more detail. Likwise west out to Burford. Many tracks and paths need completing or filling in: mainly places that are muddy and overgrown, left for better weather or others :-)

Rivers and streams are generally poor for lack of a good way to survey: anyone with a gps-enabled radio controlled model boat ? :-) I gather Richard has done most of them via his http://www.npemap.org.uk/ , but I have found the positions pretty approximate. And, I think, plain wrong in at least one case. The other issue is with the width of the rivers. The default rendering on Osmarender IIRC made the Windrush through Witney appear to cover paths and service roads on its banks, so I started guesstimating the width. In most cases, I think that I have them too narrow: I have one of the cheap sonar "tape measures" which I may eventually remember to take out: it might just be able to see an echo from a tree on the opposite bank and give a better idea of the width. Otherwise I suppose basic triangulation would work, but would take too much time and effort :-) Of course, when we can walk or cycle both banks, it is a bit easier...

Minster Lovell now pretty well complete, at least for basic mapping.