Satin spar

Satin spar, also known as feather gypsum, was a variety of gypsum that had a sparkling sheen. It was mainly used in carvings.

Description
This ornamental stone was too soft for jewelry but accepted a good polish. Satin spar was naturally white, pink, pale orange, or pale brown, but could be dyed to almost any solid hue (this process ruined its sparkle, however). A typical stone had a base value of 10 gp.

Powers
These stones could partially protect against magic missiles if worn, carried or touched at the time of missile impact. One satin spar could absorb one half the damage of one magic missile, vaporizing in the process.