— 254 F., A. Genth’s Contributions to Mineralogy. 
sand; besides, if we observe any cavities in such gold, we find 
the sharp edges of crystals, etc., in the same, rounded in a simi- 
lar manner, just as if the whole piece had been subjected to the 
action of acids, which in reality seems to have been the case. 
believe that this is the most natural explanation, because it tells 
us at the same time, to what source we must trace the gold, 
which we find in the veins passing through these formations. 
The greatest difficulty presents itself by inquiring into the 
nature of the solvent. I do not believe it is very probable that 
the gold has been carried off as a silicate of gold, or by the action 
of chlorhydric acid upon the sulphid. What seems to me most 
reasonable, is that it was-dissolved as terchlorid of gold. If we 
remember, that the decomposition of pyrites, one of the most 
n accessory constituents of diorite, produces sulphuric 
acid, which in the presence of the never wanting chlorid of 
sodium and an higher oxyd of manganese may liberate small 
quantities of chlorine, the most powerful solvent of gold, we have 
at least a very plausible explanation. 
After penetrating the decomposed diorite the solution of gold, 
passing down the veins, comes in contact with reducing agents 
and is reprecipitated again, frequently in crystals or crystalline 
forms. I shall farther below make a few remarks about the sub- 
stances which precipitate the gold, in veins as well as in beds. 
_An almost positive proof that the gold in the veins of the 
diorite formation originates from the adjoining rocks is the fact 
that the deeper the diorite is decomposed, the deeper the gold is 
found in the veins. Many of these veins do not contain any 
2g - 
r they prove that the gold must have been 2 
a. From Whitehall, Spotsylvania Co. Va.,—shows gold asso- 
ciated with tetradymite, Acabaite and quartz. The gold is cry® 
me, Be er dine nell 
to th and 
