What is an identification test for minerals that is not generally a reliable test?

Believe it or not color is the least reliable identification method for a mineral. While it can be very helpful when used along with other types of identification tests, color alone proves nearly useless. This is because several different minerals can have the same color or one mineral can be several different colors. Generally this is due to the varying chemical compositions a single mineral can take on. For example, iron, depending on its oxidation state, can cause the same mineral to be several different colors, leaving the examiner with a large list of possibilities. Also, in another example, there are hundreds of minerals that are known to be green so again the possibilities are endless.