Below is a collection of online resources that I've found helpful while learning how to ID minerals in hand samples and thin section. I don't have any involvement in the creation of anything linked below but wanted to highlight some great online resources from others to navigate through!
Thin Section
Matt J Kohn is a professor at Boise State who has a lot of great videos posted talking through different thin section examples.
Alessandro Da Mommio's website that has a lot of great visual aids and explanations of relevant processes.
Textbooks
Open source textbooks by Dexter Perkins of University of North Dakota. Both are available as PDFs, but the website has the most up to date text
Mineral ID & Structure Databases