Mineral Synthesis. 169 



Hornblende and tourmaline were regarded as outside the 

 field of artificial formation, because all attempts at their pro- 

 duction were fruitless. 



Von Chrustschoff, of St. Petersburg, who had already won 

 a reputation in this work, attempted the formation of horn- 

 blende. He found the weak points in the glass tubes were the 

 terminations, so he improved this by prolonging the tube into 

 a long neck and funnel, so that its thickness was equal 

 throughout. The tube held about twenty-five cubic centi- 

 meters of liquid. He next constructed an oven which would 

 hold a number of these. P^ach tube was inclo.sed in an iron 

 capsule, and these placed in an iron retort, surrounded by a 

 second iron cylinder. The space between the two was filled 

 with sand. The whole apparatus was covered within and 

 without with asbestos, and heated by two to six Bunsen gas 

 burners. In the tubes was placed a stiff gelatinous mass 

 made by mixing a three per cent solution of coloid silica, 

 an aqueous solution of alumina, iron oxyhydrate, lime w'ater, 

 fresh magnesia hydrate, a drop of soda lime alkali. Out of 

 the five tubes, three remained unbroken at the end of three 

 months. The heat w^as turned off" at night, and so was inter- 

 rupted; the temperature maintained was 550 degrees centi- 

 grade. 



At the end of the period, examination of the contents 

 revealed a number of hard grains of dark color. These were 

 found to be prismatic crystals, one millimeter in length and a 

 quarter millimeter thick, perfect enough to be measured. All 

 the chemical, physical and optical properties were identical 

 with those of hornblende. The crystals were of greenish-color 

 pleochroic, and showed beautiful zonal structure. 



Associated with these were a number of crystals determined 

 as pyroxene, probably diopside ; colorless grains, possibly anal- 

 cite ; quartz crystals, two millimeters in size, with fluid inclu- 

 sions; thin rhombic tables of orthoclase of the adularia t>pe. 

 This is the association one would expect to find in a natural 

 rock, and so makes a mineralogically and geologically perfect 

 synthesis. 



[to be continued.] 



