BULL. GEOL. SOC. AM. 



VOL. 28, 1916, PL. 27 



THIN-SECTION OF DOLOMITIC PHASE OF FRANCONIA SANDSTONE 



The dolomite rhombs average .f> mm. in diameter. Tliey incliido quartz grains, the nngular white 

 spots, showing that tlie dolomite grains grew in the sediments. 'I'he matrix is opainie, liinonitic. 

 structureless, and includes numerous angular, dustlike pni'ticlos of (|u:irt/.. Tlie wiiite areas around 

 the dolomite rhombs are holes in the slide. 



