Some collectors enjoy seals because of their stones. Seals can me made in a wide variety of materials and can be very beautiful. They can also be incredibly expensive A good piece of chicken-blood stone, for instance, can cost just as much as buying a house. It can be extremely difficult to tell one variety of stone from another and fakes abound, so unless you have a stone with an unimpeachable provenance (and even these can be forged), I don’t recommend collecting stones as an investment. If you collect because of the beauty of the stone and it brings you pleasure, then nothing else matters.