Yes the silver Canadian dimes seem to be the most abundant for me as well. Since starting CRH in May I have found 4 so far and almost 200 silver rosies and 22 mercs. So yes they are pretty rare, but they are out there!
Just remember any pre 1967 Canadian dime is 80% silver
1967 are either 80% or 50% silver and there is really no way to tell them apart from what I understand and when selling them they are all considered 65% silver(crazy I know).
1968 are either 50% silver or 99% nickel and you can weigh them if you cannot tell by looking at the rim.
Also the other day I noticed that the Canadian dollar is worth more than a US dollar by .01, which means all Canadian dimes are keepers