Star diopside

Star diopside was the asteriated form of diopside, a durable gemstone.

Description
Diopside was a hard, durable gemstone that was usually found in unattractive colors, such as very dark green or brown. Occasionally, mountain- and streambed-pebbles would yield crystals of lighter shades of green that produced attractive semi-precious stones (see dioptase). The most prized specimens of diopside exhibited four- or six-ray stars when cut and polished. A typical specimen had a base value of 100 gp.

Powers
Star diopside had a very specific and unusual property of flashing repeatedly whenever it was within 10 ft (3 m) of illusion/phantasm magic. It was thus in demand for decorating entryways to courtrooms, temples, and homes of the well-to-do.