;J50 CHEMICAL EXAMINATION OF MINERALS 



W. Henneberg found in his experiments on the effect of heat on zircon, that the con- 

 densation after ignition, was as 10,000 to 9798. The density before being 4-615, and 

 after 4-71; and also observed, that at a certain stage, the crystals exhibited a phospho- 

 rescence. In my experiments, raising the crystals to a white heat in a platinum crucible, 

 I did not remark any phosphorescence, which was carefully looked for, and the tempera- 

 ture gradually raised. The density of the crystals before and after ignition, was 4*595 

 and 4-62, corresponding to a condensation as 10,000 to 9946. 



Rose, in the last edition of his Handbuch, suggests the fusion with bisulphate of ammonia, 

 which has never been applied to zircon, as a probable means of its analysis. I performed 

 the experiment very carefully upon 0-961 grammes of the finely pulverized mineral, keeping 

 it as loner a s possible in contact with the re-agent; but with negative results. The inso- 

 luble portion was silicate of zirconia, very white and almost entirely free from iron, while 

 about 1-5 per cent, of zirconia dissolved out, and was precipitated along with the iron. 

 This method, though not applicable to the analysis, may serve to free silicate of zirconia 

 from iron, should it be required to prepare this salt from impure zircon. 



3. On (he Occurrence of Gold in Pennsylvania. — In the spring of 1851, an earth was 

 given to me for examination, of which the locality was not exactly stated, but which was 

 said to have been taken not far from the city, in which gold was detected. The earth 

 was said to have been obtained in digging a well. Several months later, while in Reading, 

 I met with a notice in a German newspaper of that place, which stated that some time 

 previously an earth had been found in digging a well, upon the land of Mr. Yoder, Fran- 

 conia township, Montgomery county, which proved, upon examination, to contain gold. I 

 have no doubt but that this is the locality of the earth which I examined. Several rocks 

 from the neighbourhood were submitted, consisting of clay slate rock, ferruginous quartz, 

 decayed in places, containing pyrites and magnetic oxide 'of iron sand. In most of these 

 gold was detected in traces. Some specimens contained no gold whatever. The earth 

 from the well, which was more particularly examined, consisted of sand and gravel, coating 

 in some places fragments of shale or other rock. A careful examination of these with the 

 lens, detected a rather thick spangle of gold adhering to the gravel, and a small rounded mass 

 of a white malleable metal which proved by a microchemical investigation upon half of it 

 to be native tin, which occurs only, according to Dana, in small grayish white metallic 

 grains along with Siberian gold. It melted before the blowpipe, was oxidized by nitric acid, 

 the resulting oxide being insoluble in tartaric acid. Dissolved slowly in HC1, to which so- 

 lution IIS gave the yellowish brown precipitate SnS+SnSo. This occurrence of native tin 

 is strongly opposed to the supposition of fraud in the earth examined. Separating the rock 

 and washing, gave a further quantity of gold spangles very fine, and mingled with pyrites 

 and magnetic oxide of iron, together with more spangles of native tin. One and a half 

 pounds of the original substance, from which these spangles were removed, after separa- 

 tion of the rocks and concentration by washing, were melted with twice their weight 

 of litharge, (previously tested for gold,) and a small quantity of charcoal powder. The 

 resulting button of lead was cupelled (adding to the lead the gold already found) and the 



