This is an ebook reference source. Search for your mineral in the Box labelled Search Within This Publication. Great resource, but not all minerals can be found here.
This is a great page to learn about the trade and value of your mineral, but may not be much help in putting together your trading card. Some minerals have "Factsheets" which would be helpful. USE WITH CAUTION.
It will help if you've already learned whether your mineral is a silicate or non-silicate mineral. Less information, but the articles can be translated into Spanish.