ARTIFICIAL PRODUCTION. 78 
Gaiidin,« during 1869, obtained corundum by the decomposition of 
potash ahun by charcoal, and also by fusing amorphous alumina in 
the oxyhydrogen blowpipe flame. The melt, when cooled, has the 
hardness of corundum, but a specific gravity of only 3.45. 
Fremy and Feil « produced a corundum in 1877 by fusing together 
minium (t^PbO.PbOo) and alumina in siliceous earthen crucibles. 
In this reaction a lead aluminate was first formed, and this, uniting 
with the silica of the crucible, formed a lead glass, liberating at the 
same time the alumina, which crystallized out as corundum in the 
form of hexagonal plates. The specific gra^dty of these crystals was 
4.0-4.1. By the addition of a chromium salt a ruby corundum was 
produced which had the color and hardness of the natural ruby and 
which, like the natural ruby, was decolorized "temporarily by lieating. 
They also obtained corundum in the form of sharply crystallized 
rubies by fusing together in a clay crucible, covered with another 
inverted one, equal weights of ahunina and barium fluoride with a 
little potassium bichromate.'' 
St. Mennier '' in 1880 heated to redness in a porcelain tube alumina 
chloride, magnesium, and water vapor, and obtained a very minute 
crystal which resembled corundum, but lie was not able to determine 
it exactly. By substituting zinc for the magnesium in a similar 
experiment, and also by leaving out the metal altogether, similar 
results were obtained. 
In 1882 H. Grandeau '^ obtained corundum in the same manner as 
Debray in 1861, and he called attention to the formation of a double 
phosphate of alumina and potash with the corundum. 
By treating freshly precipitated alumina, Al3(OH)3, at a tem- 
perature of 300°, with water containing a trace of ammonium fluor- 
ide, Bruhms '■ in 1889 obtained small hexagonal crystals of corundum 
Avith ])yramidal terminations. 
Lacroix ^ has shoAvn that ])y the destruction of acid inclusions in 
certain magmas, as basalts, trachytes, and andesites, corundimi, zircon, 
diaspore, etc., were produced. He states that this may be the origin 
of the corundum and zircon in Haute-Loire. 
Friedel >' in 1891 described experiments in which amorphous alu- 
mina Avas heated in a closed tube in a solution of soda to a tempera- 
« Comptes rendus, Acad. Sci., Paris, vol. 85, 1877, p. 1029; Dana, INIinei-alosy, 1892, 
p. 218. 
'' Fouque and Levy, Synth, min. et roches, p. 223. 
'■ Fouque and Levy, Synth, min. et roches, p. 223 ; and Comptes rendus. Acad. Sci., 
Paris, vol. 90, p. 701. 
'^ Comptes rendus, Acad. Sci., Paris, vol. 95, 1882, p. 921. 
« Neues. Jahrbuch fiir Mineral., vol. 2, 1889, p. 62 ; Am. Naturalist, July, 1890, p. 671. 
f Bull. Soc. frang. de mineral., vol. 12, 1890, p. 100. 
•" Bull. Soc. franQ. de mineral., vol. 14, 1891, p. 7. 
