ABT. 19. MORDENITE — ROSS AND SHANNON. 19 



EXPLANATION OF PLATES. 



Plate 1. 



LTpper left. Geodal mass of cottony type of mordenite with chalcedonic shell. 



Upper right. Analcite crystals in cottony mordenite. 



Lower. Argentine calcite inclosed in compact fibrous mordenite. Note thin 

 shell of heulandite which lines the cavity. The small black specks on or near 

 the calcite plates are small dendrites of manganese oxide. All natural size. 



Plate 2. 



Upper. Small pure mass of compact, felted-fibrous mordenite filling gas 

 cavity in andesite. 



Center. Two specimens of amygdaloidal andesite containing amygdules of 

 mordenite, heulandite, and chlorite. 



Lower. Mordenite-filled cavity, all except the central part of the loose- 

 textured mordenite being saturated with granular quartz. All natural size. 



Plate 3. 



Upper. Natural thin flattened analcite crystals from between plates of 

 argentine calcite. Photographed between crossed nicols to show anomalous 

 birefringence and division into sectors. X20. 



Right. Argentine (calcite) coated with quartz spicules and bearing small 

 flattened analcites. Natural size. 



Lower. Tufts of mordenite fibers attached to groups of quartz spicules pro- 

 jecting from platy argentine calcite. Natural size. 



