Eakle.J 



Colemanite from Southern California. 



37 



w = — 44{182|. The edge between \131\ and [ 110 j was replaced 

 by a narrow face which was somewhat rounded, and did 

 not lie exactly in the same zone with these two forms. 

 The symbols are the nearest simple ones to agree with 

 the readings, although the measured and calculated angles 

 do not closely agree. 



<f> p 

 Measured 0.16 G3°4P 



Calculated 0.09 (14 16 



Crystal Habit. — Four quite distinct habits are noticeable, and 

 these will be designated as Habits 1, 2, 3, and 4. 



Habit 1. — Crystals of this habit are characterized by a broad 

 base (001) and rear orthodome (201), the two faces meeting in 

 a long edge, almost the width of the crystals. The prism (110) 

 is long and almost meets the base, the unit pyramid (111) being 

 merely a narrow truncating form. The pyramidal forms are 

 small and grouped at the extreme right and left corners of the 

 crystal. The clinodomes (Oil) and (021) are often absent. 

 This habit exhibits the monoclinic symmetry of the crystals in a 

 more pronounced way than the other habits do. This type of 

 crystal is seen in Figure 1, Plate 2. The rear orthopinacoidal 

 face (TOO) is generally broad like the dome (201). The clino- 

 pinacoid occurs only as broad cleavage faces, and many of the 

 crystals are cleaved into tabular plates parallel to this form. 



Habit 2. — In this habit the base and orthodomes are either 

 very narrow or completely wanting. The clinodomes and rear 

 pyramids are large and about equal in size. The crystals have 

 a characteristic pointed appearance at the ends of the ortho- 

 diagonals, the points being truncated by small natural faces of 

 the clinopinaeoid. Most of the crystals seem to be of this habit. 

 Figure 2, Plate 2, shows this habit. 



Habit 3. — In this habit the front upper terminal faces are 

 quite small, while the unit prism faces and the orthodome (201) 

 are large. This gives a somewhat flattened appearance to the 

 crystals, and at the same time causes them to be pointed at the 

 ends of the vertical axis. This habit is quite striking, and the 

 specimens are quite suggestive of dog-tooth spar. This type is 

 seen in Figure 3, Plate 2. 



