The National Library of Wales holds the world’s largest collection of journals relating to Wales, and Welsh Journals Online provides free access to a large range of these. The back-numbers of up to 50 titles will be available here, ranging from academic and scientific publications to literary and popular magazines, and new titles are regularly added. Complete runs of each title have been included; the most recent issue available depends on the publisher, and will vary from title to title.
Needless to say, most journals contain mining articles:
http://welshjournals.llgc.org.uk/
Cutting coal in my spare time.