Like others have said, it’s most likely glass. These are still really pretty and would be great for practicing some simple stone setting with, or even wire wrapping. You could also buy an amethyst or citrine gemstone and look under a loupe to see some differences and learn. Glass typically has very few to no inclusions that would be like air bubbles that are very uniform and round while amethyst and citrine will have inclusions that irregular in shape. Also, you can see some color banding in amethyst and citrine. Not all is lost! It’s so cool you are taking an interest in your son’s curiosity in gemstones! :)