392 PROCEEDINGS OF THE AMERICAN ACADEMY. 



Through the kindness of Professor B. K. Emerson we were given the 

 opportunity of studying a suite of specimens of the Athol bahingtonite 

 belonging to the Amherst Mineral Cabinet, and the result of our exami- 

 nation is to establish Shepard's original determination as correct. Ac- 

 cording to Professor Emerson the locality is no longer accessible, and a 

 very small amount of the mineral is believed to be extant. 



The material studied consists of a large matrix specimen and a num- 

 ber of small crystals, all apparently detached from the larger mass. 

 This is a fragment of chloritic gneiss bounded on two surfaces by what 

 were clearly veins. These faces are coated with a thin drusy layer of 

 dark green epidote, upon which, on one side, the babingtonite is implanted. 

 It is in brilliant shining black crystals, most of the faces striated and 

 curved or warped, the largest crystal not exceeding .3 cm. in diameter. 

 Only by using the very smallest crystals, on which the curvature of the 

 faces was least marked, could satisfactory measurements be obtained. 



With the babingtonite are a number of sharp cubes of perfectly fresh 

 pyrite. These were deposited before the babingtonite, as is shown by a 

 narrow vein of the latter mineral traversing one of the pyrite crystals. 

 There are also several minute rosettes of prehnite implanted on the 

 babingtonite and a small amount of a platy zeolite which from incomplete 

 tests appears to be apophyllite. 



Six crystals were measured and the following forms determined : 

 a (100), b (010), c (001), h (110), g (2T0), f (320), s (Oil), o (011), 

 d (101), and w (025). 



The following table shows some of the measured angles, together with 

 the calculated values and Dana's corresponding approximate values. 



The forms h, o, and w were each observed but once. The others are 

 generally all present and form combinations of the habit shown in Fig- 



