Bismuth, officially discovered in 1753 by French scientist Claude Geoffroy, is the chemical element Bi. It is naturally reddish-white to a creamy-white. It tarnishes beautifully into an iridescent bluish, pinkish, purplish and/or yellowish metallic color. It's soft, with a hardness of 2 - 2½.  All commonly seen in stair-step specimens are lab-grown.
 
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* Sizes, shapes and colors my vary due to being a natural stone, being hand-carved and/or difference in computer monitors.