"To muse, to creep, to halt at will, to gaze ... such sweet wayfaring" William Wordsworth
I love the names of places I read on your blog! :-)
If the mine only closed in 1920s, then it either lasted a longer time than most, or was a later starter than the 1860s.
I think the initial mining was alluvial and this was followed up with reef mining from the 1870s and lasted into the 1920s sometimes longer. During the depression a lot of the mines got another work over.