I'm working on something similar to this for prospecting. Unfortunately a major issue is that even minor impurities can radically alter the appearance of minera

I'm working on something similar to this for prospecting. Unfortunately a major issue is that even minor impurities can radically alter the appearance of minerals. Google corundum if you want a good example. Another issue is that people tend to post pictures online of exceptional samples which are pretty much by definition very different from what one would expect to find in nature. Finally, visual inspection is often not sufficient to determine what mineral something is, even if you know exactly what to look for; other tests such as scratch tests or chemical tests, etc are used to make the final determination. All in all you're probably not going to be able to make a general rock identifier that gives useful results for everything. You may get away with something more limited, but even then you're going to need a better database of images than google for training. I agree though it would be cool to have.