90 
MINERAL VEINS. 
the lead lodes of Wales, Derbyshire and the North of England ; N.E. 
and S.W. is that of the famous lead and silver lodes of Clausthal in 
the Hartz, Schemnitz in Hungary, and Linares in Spain. Those 
following the above directions are in some of our districts termed 
right running veins,” whilst occasionally another group coursing to 
a different point of the compass will also bear ores,—as with tne 
^‘caunter” copper lodes of Cornw’all, which bear E.S.E. and W.N.W. 
Ihose again which cross the first-mentioned at a great angle, and are 
thence termed cross-veins or cross-courses,” are very commonly quite 
barren, whilst in parts of Cornwall they are notable as carriers some¬ 
times of iron ores and sometimes of richly argentiferous galena. In 
certain tracts, such as the Erzgebirge, or ore mountains of Saxony, 
several distinct groups of lodes have been proved to differ no less in 
their strike or direction than in the character of the minerals which 
they contain. 
When followed, either horizontally or in depth, each single lode is 
found to be subject to the variations above-mentioned, as far as regards 
its size and the proportion of valuable contents. Thus the same lode, 
which in one district of the mine contains nothing but quartz, calcite, 
or barytes, (the “spars” of the miners) will elsewhere yield a goodly 
quantum of copper or of lead ore, or perhaps exhibit for a space 
scarcely anything else than a pure course of metalliferous minerals. 
Hence arise the sudden turns in the history of mines, the rapid influx 
of wealth, the uncertainty of its lasting, and the necessity for well 
managing the reserves and constantly farther exploring a lode that 
has been successfully opened upon in some part of its course. Many 
of the varieties of structure which are exhibited in the succeeding 
cases of the museum may happen to occur in different portions of 
the same vein. Two minerals confusedly crystallized together, in a 
manner not always very explicable by our present chemical knowledge, 
or one of them deposited at the sides of the lode upon the already 
consolidated crystals of the other mineral, these are some of the 
simpler appearances that present themselves. In Derbyshire, Corn¬ 
wall, and Saxony beautiful specimens are produced, which indicate the 
succession of a number of crystalline minerals each placed afresh on 
an earlier crystallized surface. The banded or riband veinstone thus 
affords a chronology of the various substances forming it, which may 
now and then be only partially true, but which sometimes holds good 
for the whole vein or system of veins. Thus calc-spar and rich silver 
ores are apt to be the most recent of all the contents in the lodes of 
Freiberg, of Mexico, and the Southern Hartz. 
Many peculiarities are coupled with the succession of the minerals ; 
sometimes it is observable that the newer mineral coats or invests only 
the crystals of some particular substance previously formed, entirely 
avoiding others ; or it will be found attached only to certain sides of 
the older crystals, as if it had been carried there by a current setting 
in a particular direction, or had been deposited under the influence of 
polar forces. The structure which our miners term “ comby ” gives 
proof, with its ranges of prismatic crystals shooting from the side 
towards the interior, that some of the veins have been rent open at 
several successive periods nearly along the same lines ; it is especially 
observable in some of the iron-courses, along which there are other 
