112 THE MINERAL WEALTH OF BRAZIL
The average during the 1920-9 period was 65,700 metric tons, that of the 1930-4 period 22,870 metric tons and the 1935-9 period, 1,040 metric tons. In 1940, lhe imports totalled 67 metric tons 37 metric tons of which was salt for industrial applications while 30 metric tons was table salt. In the previous year, the former amounted to 95 metric tons and the latter 46 metric tons.
Pertinent to these changes are the export and import prices of thd various types of salt. The export price (FOB Brazil) in 1939 was 452 milreis per metric ton while the import price (CIF Brazil) of the industrial salt was= 366 milreis and that of table salt 1,038 milreis. In 1940, the corresponding prices were 394 milreis, 593 milreis and 1,178 milreis.
Although it is difficult to completely trace down the imports of prod-i nets made from salt, it is of interest to point out two of some importance, sodaii ash and caustic soda, the first because it comprises the largest mineral salt in port and the latter because of the presence of one plant in Brazil, the plans tos construct another and the large annual demand in Brazil which continues to be. filled from overseas sources in preference to its manufacture domestically des-] pite the presence of abundant raw material. In 1940, the imports of soda ashf amounted to 23,378 metric tons valued at 17,736 contos while that of caustic^ soda amounted to 31,515 metric tons valued at 48,007 contos. Domestic production of the latter amounts approximately to 1,500 tons annually.
17. SEMI-PRECIOUS STONES
The use of semi-precious stones dates back to the days of Babylon, their most important use at the time being for the manufacture of seals. Some by their appearance were credited with having medicinal or magic powers. To- day, practically the only use is for adornment and ornamentation.
The characteristics of a gem are: beauty or splendor, durability (de-pending principally on the hardness of the stone), rarity, fashion (temporary and variable) and portability.
The first of these qualities is brought out by cutting which may be faceted, or by engraving, which may be in cameo, or carved or curvette. The principal lapidary center for colored gems is Idar-Oberstein, Germany. In Brazil colored stones are lapidated in Belo Horizonte (Minas Gerais) and in Rio de Janeiro.
• No satisfactory studies have been made on this subject, the interested parties limiting themselves only to rudimentary and superficial workings of the deposits. Gems are sometimes discovered accidentally in the search for other useful minerals. During the past two centuries, Brazil has produced a number of colored stones, principally beryls and tourmalines, the production of which though not very significant, still continues.
The gem trade operated, until a few years ago, under complete free- dom and for this reason, no statistical data as to turnover or production are