Now, all the parts of the stone in which the figured quartz is directed
in the same manner, or regularly placed in relation to each other,
present that shining appearance to the eye at one time, or in the same
point of direction. But there are parts of the mass, which, though
immediately contiguous and properly continuous, have a different
disposition of the figured quartz; and these two distinguished masses,
in the same surface of the polished stone, give to the eye their shining
appearance in very different directions. Fig. 3. shows two of those
figured and shining masses, in the same plane or polished surface.
It must be evident, that, as the crystallization of the sparry structure
is the figuring cause of the quartz bodies, there must be observed a
certain correspondency between those two things, the alinement (if I may
be allowed the expression) of the quartz, and the shining of the sparry
ground. It must also appear, that at the time of congelation of the
fluid spar, those two contiguous portions had been differently disposed
in the crystallization of their substance.
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