To do a locality search, you can type in the locality that you are looking for in the Locality search box at the footer search of any page of mindat.org.
You should not enter the entire locality name string in the search box, but rather concentrate on the most unique aspects of the name (you need to enter at least three letters in the name). For example, if you want to find the "Black Bear mine" to the database you should run a location search with either "Bear" or "Black Bear" (don't search for the "Black Bear mine", the locality may have been entered as the "Black Bear tunnel", "Black Bear adit", Black Bear quarry", etc. - the Search for "Bear" will display any of these other names). The search on multiple words looks for that exact string in the locality. For example searching on "Black Bear Montana" looks for that exact string in the database. If the locality string is "Black Bear nine, Beaver Co., Montana, USA", that search would not find this locality. If you want to use this type of search, the Google mindat site search is the best search to use.
If the locality does not show up on this search (there are often slight differences in the spelling of a locality's name), then you could run another search looking higher up on the locality hierarchy (for instance the Mining District, County, Province, State, etc. that the locality is in - some of these higher localities can have several thousand entries so the lower you are in the hierarchy, the faster the searches will run). You could then look and see if your locality is included as a sub-locality.
The following are the primary abbreviations used in mindat locality strings. Other abbreviations are not used (ie no province or states are abbreviated)
Co. - County (only as political hierarchy, not if in site name) incl. - including Mt - Mount Mtn - Mountain Mts - Mountains No. - Number St - Saint Ste - Sainte (in French locality names) twp - township UK - United Kingdom USA - United States of America