Linda Armbruster, age 15, of Freeport, Ill., for her question:

WHAT IS LAPIS LAZULI?

Lapis lazuli (pronounced: lap is laz you lie) is an azure blue mineral that is sometimes called lazurite. The mineral is made up mainly of aluminum, sodium, silica and sulfur. Its beautiful color makes it valuable as an ornament.

Ancient Egyptians used lapis lazuli in their jewelry, as did the Romans. It was also once the source of ultramarine, a blue pigment used in artists, paints. Today this pigment is made chiefly by chemical methods.

Lapis lazuli occurs in masses of fine grains and in crystals. Most of these deposits are in beds of limestone. The best specimens come from Afghanistan.

Lapis lazuli is sometimes flecked with brilliant, shining spots. It is these flecks, called pyrite, which help to identify genuine lapiz lazuli.

Ancient peoples believed that lapis lazuli had medicinal value. They ground the mineral to a powder which they then mixed with milk. The mixture was used as a dressing for ulcers and boils.