Bismuth is an elemental metal used in stomach medicine, and as safe alternative for lead in fishing weights and shotgun pellets and so on. Can you have such a thing as a safe shotgun pellet? Anyway...
These crystals are formed naturally on cooling from a molten state in almost 100% pure bismuth. The conditions for this to occur in nature wouldn't happen, and so these have been given a helping hand, being made in small vats by a cackling alchemist in England. The metal is silvery grey in colour, but forms a colourful oxidised layer.
Crystal around 4-5cm.