Note on the Formation of Gold Ore. — von Krantz. 101 
them, but that together with the associated quartz they were 
rolled to their present positions in river beds. Enclosed in an 
equal bulk of lighter rock the transportation of the metal 
A\-ould be much more easily accomplished. As for the supposed 
reenrichment of washed-over gravels, this is only reported in 
districts like the Urals and the older California workings where 
the methods were crude and only perhaps 50 per cent, of the 
gold was saved originally. It would not be surprising if in 
such localities the gold particles, by reason of their high spe- 
cific gravity, should again be collected at the same level by 
circulating waters, and thus (in the Urals after a period of 
about 25 years) make possible, with improved methods of 
working, another exploitation of the old ground. One fact, 
however, is worthy of note : small, well-formed, sharp-angled 
crystals of gold are frequently noticed, and for these the the- 
ory of formation in the places where they are found seems the 
most natural. 
From the statements just made it is plain that we can by 
no means prove that gold cannot be dissolved and redeposited 
in secondary deposits. But I intended to suggest that al- 
though the theory of chemical formation may not be satisfac- 
tory for ordinary secondary deposits, yet the occurrence of 
large nuggets is susceptible of ready explanation. In pri- 
mary deposits it is quite another matter. To what extent we 
are obliged to accept the theory of deposition from solution I 
will endeavor to show in the following paragraphs. 
If we wish to acquire a correct apprehension of the condi- 
tions governing the deposition of gold we must, first of all, 
consider its paragenesis. Henry Louis has with great care 
described all the minerals with which gold is associated. Al- 
though their number is considerable, the number of those 
which can be looked upon as characteristic and universal as- 
sociates of gold is quite limited.* Among these the most 
prevalent are quartz and the commonest sulphids, such as \)y- 
rite, chalcopyrite, galenite, zinc blende and stibnite. Of these 
latter, pyrite takes the first place by reason of its wide distri- 
bution and its constant presence where gold is found. We 
«hall now endeavor to account for the common occurrence and 
*"0n the Mode of Occurrence of Gold," Min. Mag., vol. x, No. 47, 
pp. 241-247. See also Zeit. f. prakt. (ieoL, 1894, p. 329: 189.^), p. 84. 
