METAMORPHISM 351 



Economic Importance. — Gneisses and quartzites are often used 

 for building stones and road material, but marble is the metamorphic 

 rock which is the most prized, both for building purposes and for 

 works of art. 



REFERENCES FOR METAMORPHISM 



Chamberlin and Salisbury, — Geology y 2d ed., Vol. 1, pp. 426-449. 

 Cole, G. A. J., — Rocks and their Origins. 

 Leith, C. K., — Structural Geology. 

 Pirsson, L. V., — Rocks and Rock-Minerals. 



CLELAND OEOL. — 23 



