1901.] NATURAL SCIENCES OF PlIIl.A DELl'llIA. 551 



little nitric acid was added and rubbed, then poured into a capsule; 

 a second dose of nitric acid was given and worked as before. The 

 gold appeared now, after washiug with water, in its bright yellow 

 color. The acid solution, after settling, poured cleanly into a test- 

 tube, gave with a few drops of hydrochloric acid the well-known 

 white precipitate of chloride of silver soluble in ammonia. 



The gold was, as may be expected, in very thin plates, and, 

 although not absolutely pure, showed the two distinct colors of the 

 •metal — the fine yellow by reflected light, and the violet color 

 when a ray of ordinary light passed through it and was observed 

 under the microscope by sunlight. By artificial light the color is 

 modified to a greenish tint. The test of a gold-containing mineral 

 in a rock, as described above, can be made within ten minutes. 

 The microscopic part of the test is, of course, unnecessary, as the 

 gold can be seen as readily without it after the treatment with 

 nitric acid. 



The ease and quickness of this blowpipe process^^and the little 

 preparation required may recommend it to prospectors for gold 

 ore, who, we are well aware, often overlook gold-containing min- 

 erals in the absence of an easy and simple test. The above-described 

 method, if followed, may be found helpful, inasmuch as no new 

 instrument or apparatus is required. 



The finely and sparsely distributed gold compounds in the Crip- 

 ple Creek volcanic rock have a similarity in appearance to com- 

 mon pyrites. Iil volcanic rocks, therefore, wherein both minerals 

 may occur, the gold and iron compounds present cau only be deter- 

 mined by the application of the proper tests. 



