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ORE-FORMATIONS 263 
we meet with a union of at least two kinds of ore-formation— 
disseminations and true fissure veins—both of which have 
doubtless had the same origin and were formed at the same 
time <The copper is often enclosed in, or itself encloses, 
zeolites, thus clearly showing it has been introduced as an 
aqueous solution. The whole series of rocks, after having 
been fissured and faulted, has been acted upon by hot and 
cold percolating waters, which have produced much alteration, 
probably leaching out the copper from the igneous rocks, and 
depositing it where it is now found. 
The famous copper-slate of Mansfeld, in Thuringia, which has been 
worked for several centuries, belongs to a class of ore-formations which 
some have considered to be a kind of connecting link between epigenetic 
and syngenetic accumulations. The Kupferschiefer (copper-slate) is one 
of the subdivisions of the Permian system of Germany. The succession 
of deposits in Thuringia being as follows :— 
. Bunter (sandstone, etc.). 
. Zechstein (dolomite with rock-salt and gypsum). 
. Kupferschiefer (copper-slate or shale). 
. Weissliegendes (thin white sandstone). 
. Rothliegendes (red sandstone and conglomerate). 
- The ores occur chiefly in the Kupferschiefer and mostly in its lower 
portion, being disseminated usually in fine grains or occurring in thin 
layers and nests. So abundant is this fine dust-like dissemination that 
the rock when broken across gives a metallic reflection in sunlight. The 
most abundant ores are sulphides of copper, but associated with these 
occur ores of silver, zinc, lead, iron, nickel, cobalt, etc., mostly as 
sulphides or compounds devoid of oxygen. The copper-slate is black 
and bituminous, not more than two feet thick, and sometimes so hard that 
it rings under the hammer. It is often crowded with fish-remains, and 
with relics of conifers, such as twigs, cones, and leaves, the fossils 
being often encrusted with or replaced by ore. The presence of a 
brachiopod (Zizugula) is suggestive of the marine origin of the shales. 
The whole character of the strata, however, leads to the belief that 
deposition took place in an inland sea or salt lake. The origin of the 
ores has been much discussed, some holding that they are syngenetic, 
or, in other words, chemical precipitates. Those who maintain this view 
are of opinion that, during the formation of the shale-beds the water 
became occasionally habitable and swarmed with fish, which later on 
were poisoned by an abundant influx of water charged with salts of 
copper. Certainly the fossil fish of the copper-slate often occur in bent 
and contorted attitudes, as if they had been suddenly killed. Similar 
appearances, however, are met with in deposits which contain no ores. 
In the Old Red Sandstone of Dura Den, for example, whole surfaces 
of certain beds were covered with ganoid fishes, lying in all directions, 
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