On the. Paragenetic Relations of Minerals. 65 
and acid, for the atmosphere, and as regards the phosphates, 
the organic world must have acted upon them, and they are 
readily decomposed. 
Hitherto only the normal conditions of association: - in 
lodes have been considered. There are, however, particular 
abnormal phenomena observed at the intersection of lodes con- 
taining substances not naturally associated ; and where a 
lode traverses different kinds of rocks, or has the terminal 
planes for saalbands. These circumstances have a uniform 
connection with the richness of the lodes. This appears to 
be determined partly by the nature of the adjoining rock. 
Lode systems generally appear to exist in rocks, where they 
are considerably fissured, even where the fissures have been 
filled again. This appears very natural. It is very fre- 
quently observed in mining operations that, even when a lode 
has become poor or altogether deficient in ore, it again be- 
comes richer when other fissures having a certain position 
and direction run into it, even when they are themselves 
empty ; and when they run out from the lode, or it branches 
off, it is a sign that it will soon cease to bear ore. The 
opinion that the points of intersection are particularly rich 
has, in general, been abundantly confirmed by experience. 
There are, however, some exceptional instances. Minerals 
appear to have been deposited where there was a vacant 
space for them. An alteration in the composition of the 
minerals composing a lode indicates the proximity of another 
lode traversing it. Thus the occurrence of copper pyrites, 
fahlerz, and copper-blende, in the pyritic Jead and zine form- 
ation of Freiberg, generally indicates its intersection by a 
barytite and fluorite lode, and after this is passed the usual 
minerals are again found at a short distance. It is likewise 
considered that a lode will yield better the greater the 
quantity of water found in working it. The abundance of 
water and the richness of the lode are probably both results 
of the fissured state of the rock. The absence of ores in 
lodes appears likewise to be connected with a certain set of 
conditions. 
The intersection and junction of lodes, and the fissured 
state of the rock containing them, are very important, but 
VOL. LVII. NO. CXIII.—JULY 1854. 1 
