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On the Origin of Quartz and Metalliferous Veins. 353 
planes are uneven and somewhat granular. Where there is 
still cale-spar, plates of sparry iron may be seen between its 
foliated layers, by which regular cells are formed. These 
pseudomorphous crystals are partly upon calc-spar, partly 
united immediately with anamesite. 
These circumstances shew that the conversion or exchange 
goes on slowly ; so slow a process can only be conceived to 
operate in the wet way, and any idea of an effect by heat 
must be excluded. 
The encasing pseudomorphous forms of bitter-spar, which 
the sparry iron in the quartz veins in greywacke near Rhein- 
breitbach assumes, have certainly been produced in a similar 
manner. [If the fluids which had earlier deposited bitter-spar 
in these veins changed their nature—did they become irony 
—then the half-combined carbonic acid of the bicarbonate of 
iron took up the bitter-spar, and deposited in its place, as 
sparry iron, the salt of iron changed into neutral carbonate 
of the protoxide of iron. 
Little difficulty as there is in understanding the deposit of 
the frequently named carbonates in the veins, and the expul- 
sion of the one by the other ; it is, however, more difficult to 
explain the deposit of quartz by exchange. Quartz, it is true, 
presents itself in the forms of calce-spar, bitter-spar, sparry 
iron, carbonate of lead, gypsum, barytes, fluor-spar, and 
barytocalcite. It is therefore supposable, that if cale-spar, 
for example, were deposited from a solution at one period, 
and at a later period were brought into contact with a solu- 
tion of silicic acid, the former would be dissolved and the 
latter deposited. 
In this manner, however, the deposit of quartz in quartz- 
veins and in the metalliferous-veins of the Erzgebirge, could 
not well be explained, as this would assume that the one or 
the other of these minerals had existed in the veins before 
the deposit of the quartz. This would, however, contradict 
the epoch series of the vein matrices of metalliferous-veins 
of the Erzgebirge. It is, besides, scarcely to be imagined, 
that the predominating quartz, the oldest member of the ma- 
trices of these metalliferous veins, could have been deposited 
by such an exchange. 
(To be Concluded in next Number.) 
VOL. XXXVIII. NO. LXXVI.—APRIL 1845. 7 
