QUARTZ ROCK. 325 



ochre yellow, or with reddish, and even dark 

 purple tints. Where mica is present, the colour 

 is often grey ; and the presence of felspar, in the 

 same manner, often confera a pink or fle*h 

 coloured hue on the compound rock. 



' ; . .:."-. 



SYNOPSIS OF QUARTZ ROCK. 



. . 



FIRST DIVISION. 



Simple : of quartz alone. 



A. Pure quartz, resembling that which occurs in 

 veins. 



a. Hyaline. 



b. Opake. 



B. Pure quartz, compact, laminar; often very 

 finely fissile or almost scaly : sometimes laminar and 

 striated. 



C. Granular splintery ; occasionally passing into 

 the uniformly compact. 



D. Granular : with large grains or concretions. 



a. Crystalline compacted, and either transpa- 



rent or opake. 



b. Gravelly, with distinct condensed grains. 



