LAPIS LAZULI.
This stone was the sapphire of the Greeks, Romans and Hebrew Scriptures. Pliny likened it to the blue sky adorned with stars. Large quantities of worked pieces of it are found in early Egyptian tombs, and the Chinese have long held it in high esteem. Marco Polo visited Asiatic mines of the mineral in 1271 A. D., and these had doubtless been worked for a long time previous. Besides its value as a stone it was in former times used as a blue pigment, giving the ultramarine blue. In modern times not only has the esteem in which the stone is held for ornamental purposes declined but the mineral can be artificially made so as to give the desired blue color for paints and thus the use of the natural lapis lazuli has greatly diminished. It is still however carved to make vases, small dishes, brooches and ring stones and is used to a considerable extent for mosaic work. When, also, pieces of sufficient size and of a uniform color can be found, large carved objects may be made which command a high price.
The stone known as lapis lazuli as it occurs in nature is not a single mineral but a mixture of several, among which are calcite, pyrite and pyroxene. From these however it is possible to separate a mineral of uniform composition sometimes crystallized in dodecahedrons which is probably the essential ingredient of the stone. This mineral is known as lazulite and in composition is a silicate of soda and alumina with a small quantity of sodium sulphide. It is by making a substance of this composition that the artificial ultramarine is produced. The artificial is said to be as good as the natural for a pigment and can be produced for a three-hundredth part of the cost. The natural lapis lazuli has a hardness of 5½ and a specific gravity about like that of quartz. It is quite opaque. In color it is blue, varying from the prized ultramarine to paler, and at times is of a greenish shade. It is said the pale colored portions can be turned darker by heating to a red heat. When the variety from Chile is heated in the dark it emits a phosphorescent green light. The stone in Nature is often flecked with white calcite. Portions so affected are not considered as valuable as the uniform blue. Grains of pyrite are also usually scattered through the stone giving the “starry” effect referred to by Pliny.
Lapis lazuli usually occurs in limestone but in connection with granite so that it seems to be a product of the eruption of the granite through the limestone. The lapis lazuli of best quality comes from Asia, the mines being at Badakschan in the northeastern part of Afghanistan on the Oxus river. The mining is done by building great fires on the rocks and throwing water on them to break them. The yield at present is small, not over 1,500 pounds a year being obtained. The lapis lazuli from these mines is distributed all over Asia, going chiefly to China and Russia. The price realized is said to be from $50 to $75 per pound. Lapis lazuli of poorer quality comes from a region at the western end of Lake Baikal in Siberia. The only other important locality is in the Andes Mts. of Chile near the boundary of the Argentine Republic. This material is not much used at the present time on account of its poor quality but it was employed by the Incas for decorative purposes. One mass 24×12×8 in., doubtless from this locality is now in the Field Columbian Museum, and was found in a Peruvian grave. It is one of the largest masses of lapis lazuli known.
The walls of a palace at Zarskoe-Selo, Russia, built by order of Catherine II are entirely lined with slabs of lapis lazuli and amber. Pulverized the stone was used as a tonic and purgative by the Greeks and Romans. The name lapis lazuli means blue stone. Armenian stone is another term by which the stone is known in trade.
AMBER, MALACHITE, LAPIS-LAZULI AND AZURITE.
LOANED BY FOOTE MINERAL CO.
First row: Lapis-lazuli, polished (Siberia). Amber, rolled pebble (Coast of Baltic Sea). Second row: Amber, polished, showing insects enclosed (Coast of Baltic Sea). Third row: Malachite and Azurite, polished (Arizona). Malachite, polished (Ural Mountains). Fourth row: Malachite, polished (Australia). Malachite (Arizona).