ON THE TOPAZ OF SCOTLAND. 45 1 



that the topaz is contained, and in what kind of 

 repository does it occur? The tract of country 

 where our topaz is found, is said to be principally 

 composed of granite, and to contain, besides, con- 

 siderable portions of gneiss and mica- slate. This 

 being the case, it is probable the topaz will be 

 found in one, or possibly jn all these different 

 rocks. It may, however, be alleged, that proba- 

 bly the topaz -rock also occurs there, and that the 

 topaz may be derived from it. But the topaz- 

 rock is one of the rarest of the mountain-rocks, 

 and the topaz which it contains has always a yel- 

 low colour, and differs somewhat in regular form 

 from the topaz of Scotland ; it is also smaller, and 

 is never accompanied with rock-crystal or precious 

 beryl. Hence it is not probable, that the topaz- 

 rock occurs in the district of which we are treat- 

 ing. If, then, the topaz-rock is awanting, it will 

 be inquired, in which of the primitive rocks al- 

 ready mentioned we are to look for it ? Some may 

 be of opinion that it occurs in veins, in gneiss or 

 mica-slate, as is the case with the Bohemian, and 

 certain varieties of the Saxon topaz. The want 

 of all the accompanying minerals, as tin-stone, 

 arsenic pyrites, copper pyrites, iluor-spar, &c. 

 render this supposition improbable. But the to- 

 paz of Siberia agrees with that found in Aber- 

 deenshire, in having green and white as its most 

 frequent colour ; in opalescence ; in figure, being 



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