SAPPHIRES I. W. HOWARD, STATE UNIVERSITY,MISSOUI-A,MONTANA The sources, mining, sorting, grading, and properties of natural sapphires are described. Details of the preparation of synthetic sapphires are giwen and the methods of distinguishing natural and synthetic sapphires discussed. Sapphires rank high among gem stones, their value being enhanced by proper cutting. The chief commercial uses are as a bearing material i n electrical instruments and as watch jewels.
. . . . . . Introduction
Old Mother Nature has turned out crystallized aluminum oxide in three dierent forms from her laboratory; namely, (1) the transparent or translucent gem stones with names varying according to their colors, these colors being due chiefly to small amounts of other metallic oxides; (2) common coruudum which is transparent and with no very pronounced color, generally bluish grey to black; (3) emery or granular corundum which is mixed with more or less magnetite or hematite. The chief gem stones are the ruby and sapphire. The oxides of chromium are responsible for the red color of the ruby, while iron and titanium oxides give the varying colors found in the sapphire. The origin of the term sapphire seems to have been "lost in antiquity." There has been some dispute as to whether it is a Grecian word taken from the Island of Sapphire in the Arabian Sea, or whether it is of Semitic origin, the Island being named for the gem. Others have assumed that although the term was used by Moses it was imported into the Semitic language. The sapphire or o&+apos of Theophrastos, the saphiros of Pliny and the ancient Greeks and Romans, is believed to be the lapis lazuli (a very complex silicate of beautiful blue color) of the present day. The name undoubtedly suggests blue, the best tints being royal blue, velvet blue, and cornflower blue. However the name is now also applied to crystallized aluminum oxide of white, lilac, yellow, golden, pink, and yellow-green shades. The paler shades are described as feminine in contrast to the deeper, richer, masculine varieties. The name "oriental" is also prefixed, not as an indication that the gem came from the East, but as a method of distinguishing it from other minerals having the same color. For example a yellow sapphire may be called an oriental topaz, a green sapphire an oriental emerald. We also have the stellate or asteriated sapphire, the star being due to a regular arrangement of small channels or twin lamellae parallel to six sides of the prism. Light is reflected from the basal plane of the interior through these channels. Some stones also possess a fibrous or silky structure. 613
614
JOURNAL OF CHEMICAL EDUCATION
APRIL.1931
Source Siam is the original home of splendid sapphires. Sapphires are plentiful and rubies are rare in Ceylon while the converse is true in Burma. One faultless stone in Burma weighed seventy-nine and onehalf carats. However, India has given the best yield of gigantic sapphires, the largest ever reported weighing nine hundred and fiftyone carats and is said to have been in the treasury of the King of Ava in 1827. An image of Buddha cut from a single sapphire is on exhibition in the Mineral Gallery of the Rritish Museum of Natural ..lm?r;
