REPORT OF THE DIRECTOR I917 



l6l 



steeply tilted beds of red shale, and especially from those portions 

 of these beds which lie in close proximity to intrusions of amygda- 

 loidal diabase. Secondary hematite in shotlike globules and fine, 

 scaly, crystalline plates marks the stage of deposition of both the 

 barite and the calcite crystals occurring implanted on the surface, 

 and included in the body of the crystals. 



Habit. The barite crystals are thin tabular in habit parallel to 

 the basal plane, and are of nearly square basal outline owing to a 

 dominant dome habit. They vary in size from about 3 mm to about 

 25 mm, and are clear and transparent with sharp, brilliant faces. 

 A series of seventeen were selected for measurement from a lot of 

 over fifty crystals. The following forms were observed: 

 c (001), a (100), m (no), N (230), n (120), X (130), 

 L (140), (on), / (104), g (103), d (102), u (101), D (302), 

 / (113), r (112), z (in), y (122), [>< (124), ^2 (168), 5 (142). 

 Figures 2, 3 and 4 show some of the combinations observed, and 

 may be considered representative of the habit of these crystals. 



^ 2 (168). The only form observed which is noteworthy by reason 

 of its rarity is the macropyramid (168). This had previously been 

 recorded from but one locality, namely, Mies, Bohemia, 1 where it 

 was figured on two combinations, both of which are domadic in habit. 

 In the present instance the form occurs as a series of very thin planes 

 beveling the edges between o (on) and d (102) from which readings 

 could be obtained only by resorting to a method of multiple 

 reflections, five readings being averaged on each face observed and 

 the average of these averages taken as follows : 



Letter 



Symbol 



Number 



of 

 readings 



Measured 



Cal- 

 culated 



d: fi-2 



102:168 



3 



50 20' 



( 50° 20' 



3 Barite from McCormick, S. C. 



In 1909 the New York State Museum received as a donation from 

 Mr James Ross a large and interesting suite of specimens illustrating 

 the mineral occurrences constituting and associated with the man- 

 ganese ore of McCormick, S. C. Many of these consisted of stalac- 

 titic psilomelane in varied botryoidal and coralloidal shapes, on the 



Slavic, Fr., Bui. Ac. Sc. Boheme 1905, fig. 7 and 8. 



