PALACHE AND WOOD. — CRYSTALLOGRAPHIC NOTES. 651 



termination, closely resembling hornblende, are abundant in chlorite 

 schist at Chester, the only common form of this mineral there. Two 

 exceptional occurrences were noted in our collections. One specimen 

 shows a sharp vein about 4 cm. thick, consisting of margarite plates set 

 on edge on both walls, the central suture completely filled by radiating 

 needles of black tourmaline. In a second specimen black prisms of 

 tourmaline, intimately intermixed with epidote needles and plates of 

 ilmenite, occupy a calcite-filled vein in amphibolite. The tourmaline 

 is crystallized against the calcite and shows singly terminated crystals 

 with the forms a (1120), m (1010), r (10T1), and o (0221) in typical de- 

 velopment. In both of these cases the tourmaline belongs to a later 

 genetic stage than any recorded for the mineral by Emerson. 



Albite. Veins of snow-white feldspar are frequently found in the am- 

 phibolite about Chester. In cavities the crystals are sometimes quite 

 large and well formed. This feldspar was determined by its extinction 

 angles as almost pure albite. The crystals are albite twins, tabular par- 

 allel to x (T01), of pronounced pericline habit ; the forms noted (by inspec- 

 tion only) were c (001), b (010), f (130), m (1 10), M (lTO), andx (T01). 



Chlorite. Although beautifully sharp pseudo-hexagonal crystals of 

 corundophyllite and amesite, respectively the dark and light green 

 forms of chlorite common at Chester, are abundantly present in our 

 collections, attempts to study them goniometrically were quite unsuc- 

 cessful. The basal plane is alone of good quality ; the pyramid planes 

 are too deeply striated to yield any measurements. The appearance of 

 these crystals is well described by Emerson, 9 and we can add nothing 

 to his statements of the facts. 



Other Minerals. A number of other minerals are represented in our 

 collections from the Chester emery mine, but not in crystals permitting 

 of even approximate measurement. A list of them is appended, to 

 which are added four species, recorded by Emerson from the mine, 

 which we did not see : margarite, chloritoid, hornblende, talc, oligoclase, 

 titanite, calcite, aragonite, dolomite, malachite, azurite, hematite, pyr- 

 rhotite, and molybdenite, making in all some twenty-six species known 

 from this locality. 



In the large area of serpentine north of Chester Village, which, while 

 it is not in physical connection with any part of the emery bed, is be- 

 lieved to have a genetic relation to it, are found the minerals chromite, 

 magnetite, brucite, siderite, olivine, and picrosmine ; bruciteand olivine 

 are new to the region and have been described elsewhere. 10 Other 



9 Loc. cit., Lexicon, pp. 16, 61 ; Monograph, p. 143. 

 10 Am. Journ. Sci., 24, 491 (1907). 



