Hi ICLOK
Editing a mine entry is only possible for mines you've personally added; otherwise we run the risk of people changing things all over the place; which I fully accept that the vast majority of members wouldn't do, but the safeguard is there just in case.
If the mine in question is one you've added, then any page that shows a link to it; for example a mine name search, or the mines A-Z, or the 'mines by mineral type' / 'mines by OS sheet' will also show an 'edit' and 'delete' link.
If the mine in question isn't one you added, then the easiest thing is to post the revised description to the forum and one of the admins will revise it for you, and of course credit you for the enhanced description.
Hope that helps, reply here, or PM me if you need any more details.
Thanks,
simonrl
my orders are to sit here and watch the world go by