Silvergeo Manmade Bismuth Crystals are 100% Genuine Specimens. They come with a Certificate of Authenticity. The mineral is a carefully chosen piece, with a photo that shows the actual specimen you will receive. Bismuth chemically resembles arsenic and antimony. Elemental bismuth may occur naturally, although its sulfide and oxide form important commercial ores. Bismuth is the most naturally diamagnetic element, and has one of the lowest values of thermal conductivity among metals. These specimens have been man produced. This process is completed by melting the raw natural mineral at a very high temperature and allowing it to crystallise or 'grow'. Once cooled to a solidified state & exposed to the atmosphere, the crystal form reacts with the oxygen to produce these beautiful colours.