The purpose of the course is to identify common rocks and minerals and to discover their applications and their environmental impact. This fourth session of the course was reviewed according to the remarks made during the first 3 sessions. It includes new videos and very innovative educational activities. You are invited to recognize the rocks on site with your smartphone to take a photo and geolocate them, to discuss with your peers on the ground. Together, you will practice the method of identifying rocks for you to appropriate. People who have no smartphone or tablet are not forgotten, they can do the activities by returning home, on their computer from the photos taken in the field. Compared to the third session, the mobility tool has been improved.