This item is intended for low-magic campaigns. The smooth rock is colored blue-gray and is about 4“x2”x2“ at its widest points. Its only magical property is that it sparks when it touches any magic item. The most powerful magic items will produce larger sparks. If it touches an artifact, it will explode, sending high-speed shrapnel everywhere, and doing 6d6 damage to anyone within a 3' radius, and 2d6 to anyone within a 10' radius. If the rock is broken, it loses its magical properties. If it is chipped, it can only detect more powerful magical items. If it is finely polished and is undamaged, it will glow instead of spark, and will glow very faintly when touched to someone who has cast a spell within the past twelve hours. Polishing the rock takes six hours of labor and 100gp in sandpaper, cloth and fine polish.