I learned here. You can learn, too. I defer to Herschel's knowledge. Pay attention to the questions and use the interesting rocks to research the choices. Oftentimes, you will find as each question gets answered, the focus narrows. Really, I have taken rocks to geology professors who could tell me very little. The more places you visit, the more you will learn. Actually, Herschel's questions guided me somewhat. As I started to gain knowledge, I used the internet to guide my questions more. Look up blue rocks and minerals. Click on images and look for a similar rock. Read about it and the characteristics of each will be revealed, including, magnetic, translucent, soft, hard, very hard, common, rare, iridescent, microcrystalline, macrocrystalline, ....volcanic, sedimentary, conglomerate. Very soon, you will be able to actually do just as much as I can by asking pointed questions. Typically, answering questions emphatically implies expertise. I usually preface my posts with statements about my lack of expertise if I am not sure. I encourage you to stick around. Pick a sample that intrigues you. Look up the images like I suggested and then learn everthing you can about your choice. Then look at the post again and see what questions will clarify your deductions. Ask them and then use your newfound knowledge to narrow your guesses. Then, Herschel will correct things as he sees fit. And, when he does, you will learn even more.