Yes! Pier Giorgio was majoring in mining engineering and had an interest in rocks/minerals. He collected many different types of rocks on his hikes and mountain climbs. He very meticulously labeled each one with a little number that he pasted onto it. He then typed up a corresponding sheet that explained the composition of each numbered rock.
Pier Giorgio also enjoyed photography and kept very organized photo albums. On the back of each photo he wrote a caption and the source of the photo. (Many photos were sent to him from friends and so he wanted to give them the credit.)
He also filled large albums with postcards that he collected from his travels. He enjoyed postcards of beautiful churches, major works of art and other famous sights from the cities he visited. According to his sister, he was "very attentive to his postcard collection that filled many albums." On December 15, 1921, he briefly mentioned his collection in a letter to his mother: "Dear Mama, Many thanks for your post card from Verona. Today the trunk arrived. In it I found my album but not the postcards from Cassel and other places that I had left in Berlin. I beg of you: tell aunt to bring them to me without fail..."
Pier Giorgio's collections have been well preserved by his family to the present day.