Benitoite, a titano-silicate closely related to titanite, a deep blue gem from California, is so named from its occurrence on the Mount Di ablo Range in San Benito County. When cut, its beautiful blue color resembles that of the sapphire, which it exceeds in brilliancy be cause of its higher refractive power.
was valued as gem-material at a very early date and is mentioned as an article of tribute on Assyrian tablets of the second millenium before Christ. The stone is of a rich blue color and is a complex mixture of minerals, the most important constituent be ing lazurite. It was originally used to produce the pigment ultramarine. Its average hard ness is only about 5.5. Many of the old Egyp tian scarabs and amulets are made of it and a proof that its beauty was greatly prized by the Assyrians is given in a hymn addressed to the moon-god Sin, where he is said to be bright as lapis-lazulio (uknu). Some of the earliest Babylonian cylinders were of this stone and down to the present time it has been highly valued for its rich and beautiful color. One of the chief sources has been the mines of Badak shan, in the northwest part of Afghanistan, near the upper reaches of the Oxus. Still more ancient mines have been discovered in the val ley of the Kokcha, a tributary of the Oxus. These mines have been worked for about 6,000 years and are evidently the oldest mines in the world. Near Lake Baikal in Siberia, especially along the river Malaya Bistraya, there are also productive mines and material of a some what inferior quality has been found in the Chilean Andes of Ovalle near the watershed between Chile and Argentina. At this locality masses of several hundreds of pounds each have been found, but much white limestone permeates the lapis-lazuli. The stone desig nated ((sapphire) by the ancient Greek and Roman authors was probably lapis-lazuli.
Malachite is a basic carbonate of copper, with a hardness of three and one-half to four. It is an aggregate of minute crystals, is opaque in the mass and is capable of taking a very good polish. Ornamental objects of various kinds have been made of this material, its won derful variety of rich green hues and its ar tistic markings enabling the lapidary to produce most attractive effects. Most of the fine work in this stone has come from the Imperial Rus sian lapidary works at Ekaterinburg, where a wealth of vases, bowls, table-tops, etc., have
been made. The Medno-Rudiansk mine at Nizhni-Tagilsk furnished in 1836 the largest block of malachite that has ever been extracted. Its dimensions were: length, 101/2 feet, width, 8 feet, height 31/2 feet; the estimated weight was from 25 to 30 tons. As many as 125 horses were used to haul this mass from the mine to Ekaterinburg.
Amber, which the ancient Greek poets de rived from the tears annually shed over the death of their brother Phaethon by the Heli ades, is not a mineral but a vegetable substance, the fossilized resin of pine trees of far distant times; it has been and is still used in a.variety of ways for decorative purposes, more espe cially in the form of beads to be strung as necklaces or rosaries. Example of such beads have been found among the remains of the most ancient civilizations and they have been worn by almost all races and at all periods. The hardness of amber slightly exceeds that of gyp sum, being about two and one-half, and it is thus easily shaped. It is quite strongly electric and this quality may have given rise to the supposed curative effects to be secured by wearing amber necklaces and to the belief of luxurious Romans that a cooling sensation was experienced by holding an amber ball in the hand. In Moham medan countries many of the long rosaries car ried or worn by the followers of Islam are com posed of 99 amber beads. The broad dis tinction between ecleara and ((cloudy* amber, the former of a pure, light yellow hue and quite transparent, the latter, passing through different degrees of opacity, variously marked and shaded and ranging in hue from whitish yellow to light-yellow, is that commonly em ployed, but a number of special designations are used in the amber industry. An interesting feature in some amber specimens is the inclu sion in the fossil resin of insects or plant forms, that must have become imbedded in the substance while in a fluid state and thus have preserved for us the exact appearance of in sects that died thousands of years ago. Cloudy amber can be clarified by heating it in oil, the latter being absorbed through the pores of the amber and rendering it more highly refractive. Another method of clarifying is by burying the amber in sand and subjecting it to a heat of over 100° C. for a long period.