Silkstone

Silkstone was a fibrous variety of quartz similar to tiger eye which had a faint sparkle.

Description
This ornamental stone was found in many colors, yellow being the most abundant, and was cut cabochon, tumbled, or used for engraved gems. Like tiger eye, silkstone was worn as a protection from spirits, though this was more old-wives'-tale than fact. A typical stone had a base value of 10 gp.