weird question: rat obsessed with gemstone ???? + rat tax

ok yeah it’s basically what the title says. a friend gave me this gemstone so i’m not sure if it’s real but my rats are obsessed with it. i had it sitting on my windowsill and every time they go up there they snag the stone and run away with it. i wanted to see what would happen if i gave it to them in their cage and they quite literally carry it all around the cage and piss on it but also try to eat it? i got worried that they will break their teeth trying to eat it or something so i took it out of their cage. maybe they just like their treasure.