MINERALS 



Fig. 7. Synthetic zeolite A. The crystals are bounded by cube and dodecahedron faces and show 

 good penetration twins. X 16,500. (Courtesy of D. W. Breck, Linde Company) 



Fig. 8. Subbituminous coal, Gilette, Wyoming. 

 The platinum-carbon replica was obtained from a 

 collodion replica stripped from the fractured coal 

 surface. The identity of the various objects is un- 

 known. X11,000. (Courtesy of R. R. Dutcher, Coal 

 Petrography Laboratory , College of Mineral Indus- 

 tries, The Pennsylvania State University) 



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