Crown of silver

Crown of silver was the Realms name for psilomelane chalcedony, a variety of chalcedony containing many fine bands of black manganese.

Description
The black bands of these ornamental stones took on a brilliant polish alongside the silver chalcedony, so crown of silver was usually sliced for inlays, tumbled smooth, or cut cabochon. A typical stone had a base value of 10 gp.

Powers
In powdered form, crown of silver had a mundane use in preventing rust on ferrous metals when applied directly. In magic, it was used as a component of the (possibly mythical ) everbright spell. It could also be used in place of iron filings in most spells that required them, such as certain protection spells.