Robert Erickson, age 10, of Cleveland, Ohio, for his question:

What is lazuli?

Lazuli is one of nature's most beautiful stones. It captures the colors of the peacock's tail. It has a blue which is bluer than the deep, sunlit ocean. The blue fades to rich tones of violet and royal purples. There are also areas of vivid green and rich blue‑green. Sometimes pyrite is embedded in the peacock stone, adding threads and flecks of shiny gold to the colors. Pyrite is the ‘fool's gold’ that misleads so many rock collectors.

Lazuli is also called lapis lazuli and ultramarine. The scientific name for the glamorous stone is lazurite. In the dim past, it was called sapphire and was considered sacred to the planet Saturn. Lapis lazuli has been admired by man since time began. The oldest mines in the world were dug long ago in the search for the lovely stone.

Nowadays we use lapis lazuli merely for jewelry and small objects to be admired. Before the Age of Chemistry, it was essential to the artist's palette. The old masters of Europe ground its colors to make paint. The Spanish gave it the name from which we got the word ultramarine ‑ meaning from over the sea. The stones for artist's supplies were brought to Europe over the sea from Afghanistan.

Ultramarine blue was made from the rich blue of lapis lazuli. Ultramarine green was made from the greens. These colors were finely powdered and mixed with oils to make paint. A pale color called ultramarine ash was made from the powder after the vivid colors had been extracted. The old masters used this pale color as a base for delicate skin tones. Paints made from lapis lazuli are very durable. Even great host does not cause them to lose their colors.

With the Age of Chemistry, we learned how to make the ultramarine colors synthetically. Lapis lazuli is a rare stone and artists no longer have to wait for it to be brought from over the sea. Nowadays its gorgeous colors are made in the laboratory. Only an expert can tell the difference between real and synthetic ultra fine paints. The art expert must learn to tell the difference. For some crook is always ready to paint a copy of an old master and pass it off as the real thing. The expert looks to see whether the paints used are made from lapis lazuli or made synthetically. If the copyist used synthetic paints, then the expert knows the picture is a phony. For the old masters painted before these modern paints were invented.

The world's best supply of lazurite is in Afghanistan. There in the ancient mines it occurs in sizeable lumps. It occurs in small grains in Chile. The only lazurite so far found in North America is in Colorado, where it occurs in small grains embedded in dark rocks.

Lazurite belongs to the silicate family of minerals. Quartz and feldspar are also silicate minerals containing a high percentage of the element silica. Lazurite is a compound of the elements silica, sodium, aluminum, sulphur and traces of a few others. The old earth usually hides it in limestone or marble. Pyrite minerals are almost always found near the glamorous stones.