if you're interested in where mine was, coordinates at URL:

http://www.mindat.org/loc-84125.html

Several General Grant mines in US. This one looks like it's currently being cleaned up, although not a Superfund site.

Also checked Directories in the Bean's you cited and did not find Little & Harrigan surnames there that reflected mining affiliation. Could mean they were living outside county although they owned the mine. Based on past experience with mining families, found this not to be unusual. Mining towns fairly rough so as soon as owners made some money, wives wanted to move to more civilzed venues. Consequently, you might try Sacramento, San Francisco, Contra Costa, and Alameda county census' for families (latter two would normally pick up Oakland). Another reason for being in "civilization" appears to be that gold mines were the dotcom play of the era; more money made by selling shares in a mine than made by the actual mining/smelting. This meant a lot of the action was in the bigger cities, since the locals knew what the game was.

Might be of interest to see if you can find other surnames in Directories (assume you have access to the referenced Bean's) with either the General Grant or Shamrock listed with them. My experience is that the connection is usually, but not always, associated with someone in a supervisory capacity. Best bet on Directory is for Grass Valley Township which is between pages 249 and 272 in Bean's.

Good luck

Vern D