340 RED PRIMARY SANDSTONE. 



of a dark brown approaching to black, of black 

 and red intermixed, of red and white intermixed 

 in stains, or in stripes and laminae, and of a pure 

 white. The colour is disposed in the mottled 

 varieties exactly as it is in the secondary varie- 

 gated sandstone, but these varieties are rare. 

 The white, is ordinary quartz rock, into which 

 this rock passes and with which it is sometimes 

 connected. 



SECOND DIVISION. 

 Compound : of two ingredients. 



A. Of quartz and felspar. 



a. Distinctly granular, and each substance 



easily distinguishable. 



The colours, and consequently the aspects of 

 this kind, are various ; as both the ingredients 

 may be red, or white, or either may be of a dif- 

 ferent colour from the other. It also differs ma- 

 terially in the size of the grains, varying from 

 gravelly to fine arenaceous. 



b. A mixture of quartz and felspar so inti- 



mate that the latter substance is only 

 discovered by the weathering of the 



