My students enjoy using their Smartphones for this activity. They just need to download a QR code reader. I have designed this activity as a scavenger hunt and you can change the clues to post them around your school. I limit my students to how far they can go in the school and post them around certain areas. That way I can keep an eye on the groups. I split them into groups and have them find the questions on rocks and minerals that are in the QR codes. I usually do this activity as a competition and offer a reward for first, second, and third place groups. They have to write the question down and write the answers down as well. I have included the QR codes with clues, the questions and answers, and the answer key worksheet that I give my students.