Here is an interesting one. This mineral is also called ebonite. It’s a hard, moldable polished dark color of brown or black. This was early rubber. Vulcanite was produced by adding Sulphur to vulcanized rubber. It was used for combs, ornaments and buttons.
Vulcanite - pic courtesy of Wikipedia
Hard rubber fountain pin bodies, hockey pucks, battery cases and mouthpieces for clarinet and saxophone are other uses for vulcanite.