Diamonds and precious stones, a popular account of gems .. . Fig. 67.—Primitive form of Quartz. Fig. 68.—Most ordinary form ofQuartz Crystals. Crystals of quartz do not often occur of dimen-sions sufficiently great to attract the eyes of thecommon observer. Some magnificent specimens,however, are found in the ancient formations, which,as we have mentioned, are formed principally ofsilica: here indeed we would naturally look forthem ; but that which would seem much less pro-bable, and yet actually occurs, is the presence of QUARTZ. 149 magnificent crystals of quartz, of an absolute purity,in th

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Diamonds and precious stones, a popular account of gems .. . Fig. 67.—Primitive form of Quartz. Fig. 68.—Most ordinary form ofQuartz Crystals. Crystals of quartz do not often occur of dimen-sions sufficiently great to attract the eyes of thecommon observer. Some magnificent specimens,however, are found in the ancient formations, which,as we have mentioned, are formed principally ofsilica: here indeed we would naturally look forthem ; but that which would seem much less pro-bable, and yet actually occurs, is the presence of QUARTZ. 149 magnificent crystals of quartz, of an absolute purity,in the midst of rocks nearly exempt from all traceof silica; in Carrara marble, for example, and incertain gypseous formations in the south of is formed by the union of two bodies;the one, silicon, is a substance analogous to carbon;

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Keywords: ., bookcentury1800, bookdecade1870, booksubjectgems, booksubjectprec