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).
AMBER.
Few minerals have been longer in favor for ornamental purposes than amber. Among remains of the earliest peoples such as the Egyptians and Cave-dwellers of Switzerland it is found in carved masses indicating that it was highly prized. The Phenicians are said to have sailed to the Baltic for the purpose of procuring it, while the Greeks’ knowledge of it is indelibly preserved in our word electricity derived from their word elektron. The high favor in which the ancients regarded amber has hardly endured however to the present time. Were it not for its use for mouthpieces of pipes and other smokers’ articles and the occasional amber necklace to be seen, amber would hardly be known among the present generation in our country.
Amber is a fossil gum of trees of the genus Pinus and is thus a vegetable rather than mineral product. In color it is yellow, varying to reddish, brownish and whitish. Its hardness is 2 to 2.5, it being slightly harder than gypsum and softer than calcite. It cannot be scratched by the finger nail but easily and deeply with a knife. It is also brittle. Its specific gravity is scarcely greater than that of water, the exact specific weight being 1.050-1.096. It thus almost floats in water, especially sea water. It is transparent to translucent. On being heated it becomes soft at 150 degrees and at 250 degrees to 300 degrees melts. It also burns readily and at a low temperature, a fact which has given rise to the name of bernstein by which the Germans know it, and to one of the Roman names for it, lapis ardens. Rubbed with a cloth it becomes strongly electric, attracting bits of paper, etc. As already noted, our word electricity comes from the Greek for amber, this seeming to be one of the first minerals in which this property was noted. Amber being a poor conductor of heat feels warm rather than cold in the hand, contrary to most minerals. It is attacked but slowly by alcohol, ether and similar solvents, a property by which it may be distinguished from most modern gums and some other fossil ones. In composition it is an oxygenated hydrocarbon, the percentages of these elements being in an average sample, carbon 78.94, hydrogen 10.53 and oxygen 10.53. The mineralogical name of amber is succinite, a word derived from the Latin succum, juice. One of its constituents is the organic acid called succinic acid.
The present source of most of the amber of commerce is the Prussian Coast of the Baltic Sea, between Memel and Dantzig, although it is found as far west as Schleswig-Holstein and the Frisian Islands and even occasionally on the shores of Denmark, Norway and Sweden. From time immemorial pieces of amber have been cast upon the shore in these localities and their collection and sale has afforded a livelihood to coast dwellers. Such amber is called sea stone or sea amber and is superior to that obtained by mining, since it is usually of uniform quality and not discolored and altered on the surface. Owing to its lightness the amber is often found entangled in seaweed and the collectors are accustomed to draw in masses of seaweed and search them for amber. Amber so obtained is called scoopstone, nets being sometimes used to gather in the seaweed. In the marshy regions men on horse-back, called amber riders, follow the outgoing tide and search for the yellow gum. It is also searched for by divers to some extent. From the earliest times the title to this amber has vested in the State and its collecting has been done either under State control or as at present when a tax is levied by the government upon it. This tax is levied on the amber that is mined as well as that obtained from the sea and brings a revenue at the present time of about $200,000.