Christine - My home owners insurance company (state farm ) would treat silver strikes like rare coins and would insure them but the cost is way out of hand, a $500 investment for a good large fire proof safe would be the best bet, my mother-in-law has one that is 36" tall, 28"wide and 30" deep that she bought brand new for $525, it is a fire rated safe and somebody would have to try to carry the safe off to beable to have enough time to break into it.
Walt