It's not always easy to find images online that are free and OK for you to use in your presentations. Many times images may be copyrighted or have other restrictions. Let's look at an easy to use resources for finding images of rocks and minerals that you can use in your presentations.
Just a reminder - the images on Mindat.org can be used in your presentation, but you must attribute that you took them from Mindat.org.
Creative Commons Image Search
https://ccsearch.creativecommons.org/