Tall black crystals cluster on brass

Black crystals from Bahia, Brazil. This particular piece of 53 Kg is a large druzy flat crystal that is made of dozens of natural crystals that have been growing on the same matrix. Also called Morion, this crystal owes its color to a natural irradiation ... Indeed, when aluminum impurities of the quartz, are close to a radioactiv mineral, like uranium or thorium contained inside granit for exemple, the color start changing gradually. Obviously, longer is the time of exposition, darker will be the crystal, like this one! But don't worry, this beautiful mineral is dangerous only if you drop it on your foot...On brass base.