12 



SCHALLER 



less spherulites which have become brown on the surface. Other 

 specimens show "nacrite," a talcose or micaceous mineral, quartz in 

 flattened crystals, and curved rhombohedra of dolomite. 

 The calcite is found in three types of crystals: 



(1) simple rhombohedra r{ 1011 } , abundant. 



(2) crystals apparently prismatic and more fully described below. 



(3) scalenohedral crystals showing large faces of t; | 2131 S , but 

 the crystals were so rounded that no measurements were made of 

 them. Those of the second type are found on the rhombohedra of 

 the first type and are not over several millimeters long while the sim- 

 ple rhombohedra are seldom over a millimeter thick. While the rhom- 



FiG 7. 



bohedral crystals are usually smooth and bright, those of the second 

 type are very much etched and rounded, making it difficult to obtain 

 satisfactory readings. The crystals have a prismatic appearance due 

 to the presence of the negative rhombohedron ?r| 0.17.17.1 } and a 

 form vicinal to a { 1120 | and having the approximate symbol t 

 I 17. IG. 33.1 j . No prism faces were noted on the single crystal meas- 

 ured. The forms present are: e 10112}, £{0111}, ?r | 0.17.17.1 1 , 

 S: 1 11.8.19.3 ! ?, t i 17.16.33.1 } ?. The faces of most of these forms 

 were so poor that the correct symbols could not be definitely deter- 

 mined. Fig. 7 shows the general appearance of the crystal except 

 that while the intersection of two faces is here shown as a straight 

 line on the crystal they are frequently curved and rounded. The 



