Satin spar

Satin spar, also known as feather gypsum, was a sparkling variety of gypsum used in gemstone carvings.

Description
This ornamental stone was very soft 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 killed its sparkle, however). A typical stone had a base value of 10 gp.