384 PROCEEDINGS OP THE AMERICAN ACADEMY. 



ville, formerly known as the Milk Row quarry, Charlestown, and it is 

 from this quarry that the material here described has all been obtained. 

 The mineral is not abundant, and it was only after several years of 

 collecting in the fresh quarry openings that sufficient material for analy- 

 sis and adequate crystallographic study was accumulated. In addition to 

 the material now in the Harvard Mineral Cabinet, several fine speci- 

 mens from the same locality were placed at our disposal by Mr. H. I. 

 Johnson. 



The minerals commonly associated with the babingtonite are prehnite, 

 quartz, epidote, pyrite, chlorite, feldspar, and calcite. Other minerals 

 reported from the locality are laumontite, stilbite, chabazite, melanolite 

 (known only from here and a doubtful species), and chalcodite. 



Prehnite is much the most abundant mineral in the veins, always 

 lining the walls and often forming the whole vein-filling. It varies 

 in color from pure white to quite a deep green, which often fades on 

 exposure to light. It has the characteristic drusy reniform surface of 

 prehnite, the crystals rarely individual. Occasionally the crystals com- 

 posing the globular or barrel-shaped groups are sufficiently distinct to 

 show that they are tabular parallel to c (001) with edges formed by 

 m (110) and sometimes also a (100). A single specimen showed a num- 

 ber of lath-shaped crystals attached by one end to massive prehnite, on 

 which only the three pinacoids were present. Prehnite also forms fine- 

 grained granular masses of dull white color. 



Quartz is sparingly present, generally as small pellucid crystals im- 

 planted on prehnite. In one specimen the quartz is in the form of 

 capillary crystals stretching from wall to wall of small cavities in massive 

 prehnite. Most of the crystals are combinations of the common forms 

 m (10TO), r (10T1), and z (0T11) but a few were observed and measured 

 of more complex character on which the following less common forms 

 were found: d (10T2), tt (01T2), G (13.0.T3.9), s t (112 1), (9272), 

 y (4151). These forms were present as narrow truncations of edges of 

 the common forms. The alternate edges of the unit prism were also 

 truncated by planes of a trigonal prism, apparently etch faces, which 

 gave distinct readings at variable angles not corresponding to any known 

 form of quartz but near (10.1.TT.0). 



Epidote occurs quite commonly in minute yellowish-green needles 

 implanted on prehnite or coating and intimately intergrown with babing- 

 tonite and quartz. The crystals are not measurable. 



Pyrite is found occasionally in clusters of minute crystals resting on 

 prehnite or babingtonite. The crystals are too minute and too poorly 



