Sure it can be visited from all over the world, even from the bush of Australia...
Good idea this subject when you consider it's a lot easier for a non-English to write so-so English than for an English to write in whatever exotic foreign language (such as French). But it's up to them to decide if Geoforum is the best place to get information they are looking for. In my opinion the first place to get info about French mineralogy is Mindat, where you have a set of sub-forum for the main European languages.
But just think about one thing: how many of you visited Mindat message board to ask a question, even in French? It's the same thing, or possibly even worse, for people with English as mother tongue as they are used to have choice of English sites regarding whatever subject about whatever country all over the world. They prefer to stay in their dedicated forum where English is the main language. They will try to find another source of information, only if they have no other choice.
I don't think a lot of people outside French members will post in this subject. Anyway we can go on in posting messages: in the case of one of them visits the forum, even if he cannot understand one word of the other subjects, he can always have a fun with this one and mock the poor level of frenchies in English...
Cheers