Bismuth is a brittle metal with a white, silver-pink hue, often with an iridescent oxide tarnish showing as an oily rainbow mix of colours. The iridescence colours are produced by interference of light within the oxide film on its surface.
The spiral, stepped like structure of bismuth crystals is the result of a higher growth rate around the outside edges than on the inside edges and is known as hopper crystal.
Despite being classed as a heavy metal it has low toxicity and is often used as a Lead substitute in manufacturing.
Price is for a hopper crystal piece similar to those shown in the photos and vary between approximately 3.5 to 4.5cm long. Hopper crystals are very rare in the wild so these are lab grown specimens.