A GEOLOGICAL GUIDE TO MINE PROSPECTORS. 283 
solid iron. The fluor spar is known by its brilliant colors of blue, green and 
yellow. The composition of heavy spar is 34-3 trioxide of sulphur, and 65-7 of 
baryta. Calcite in a vein is a good silver indication. You seldom see a good 
vein without it. Iron is also found in the gangue matter of gold and silver mines. 
But it may be asked, are there any surface indications of silver or gold mines or 
lodes? To this we answer yes, sometimes, but not very often. At one time in 
the remote ages of the past, before the disintegration of the rocks took place, and 
before the age of the glacial drift period, most of the fissure veins might have 
been seen on the surface. But now the debris from the eroded rocks, and the 
fragments of rock that have rolled down from the mountains, and the glacial drift 
have covered the surface veins far out of sight. In Lake County, near and at 
Leadville, the glacial drift is from 30 to 309 feet deep. And of course in order 
to reach the rock you must go through that drift. This drift is found on the tops 
of the highest mountains around Leadville. I have found this drift on the top of 
the mountain that runs up from Little Evan's Gulch at an altitude of nearly 
13,000 feet. This shows, I think, clearly that that mountain has been elevated 
since the Glacial Age. So where the debris of the eroded rocks or the glacial 
drift have covered the lodes the prospector has no guide to the veins. He must 
then, in order to succeed, resort to other means. But what other means are there 
within his reach ? We answer, the mines that are already opened. From these 
he may form a pretty good idea of the place where other veins are likely to exist. 
He must study the composition of the rocks in which good mines are found, the 
character of the gangue or crevice matter, the dip and trend of good mines. All 
these things have their importance, and none of them should be overlooked. 
After a locality or a mineral bearing mountain has been pretty thoroughly ex- 
plored by shafts and tunnels, it is no hard matter to tell on which side of the 
mountain the most mineral is likely to be found. It is the opinion of practical 
scientists that as a general rule the south and southeastern exposure of a silver 
bearing mountain is better than a northern or northwestern. I give this for what 
it is worth. My own experience agrees with this, and I think it will hold good 
in all mining countries. The practical geologist, in looking for mines, will of 
course be guided by the openings that have been made by others, and from the 
blunders they have made he can learn wisdom. 
It would do the energetic prospector no harm to get himself a work on 
geology, say Steel's or Gray and Adam's, or Hitchcock's, and study it. Such a 
course would save him many a hard day's work. He would not then, as is now 
too often the case, be found digging and delving in places where, in the very 
nature of things, there can be no mineral. It is a false maxim to say that mineral 
may be found in one place as in another. It is only where geology has placed it, 
and nowhere else. — Philadelphia Mining Journal. 
