350 B. K Emerson— The Deerfield Dyke and its Minerals. 



strictly separate. Here it fills large steam pores 10-30 mm in 

 diameter, which rise vertically 10-15 cm . The walls are coated 

 with a thick layer of diabantite and they are filled with brick- 

 red and transparent caleite in layers. 



2. Epidote. — Occurs rarely low down in the prehnite; more 

 commonly in drusy surfaces in its upper part, or spread in del- 

 icate tufts of flat blades upon the sj indle-sli ip< d crystals. It 

 is included also, with interrupted crystallization, in the caleite 

 which follows upon the prehnite. The maximum size of the 

 crystals is 3 mm . They are mostly thick plates, and under the 

 microscope show as brilliant luster and as rich dark green as 

 the specimens from the Dauphiny. It encloses as an aggre- 

 gate prehnite, sphalerite, chalcopyrite and caleite, but the 

 separate crystals are perfectly pure and transparent. The 

 thickest crystals are deep pistachio green ; the thin plates are 

 deep brown-red, sometimes half colorless. 



Axinite.— Jet black, opaque crystals, the largest 10-12 mm 

 in length, imbedded in prehnite and caleite and resting on 

 prehnite. The crystals are thick plates, resembling, as do 

 many of the minerals found here, the simpler forms from 

 Bour d'Oisans — the faces P and u large and striated verticaHy, 

 and P also striated horizontally parallel to the intersection edge 

 of P and r. The face r is smaller and striated horizontally. 

 Earely the faces v, /and 5 appear. Two very distinct distant 

 cleavages, es{ - i clear under the 1 icroscope, parallel to the 

 two striatums upon P, and nearly at right angles to this face, 

 thus nearly cubical. Thin splinters show brilliant trichroism, 

 deep bottle-green, plum blue and clove brown, and are glassy 

 and easily transparent under the microscope, and entirely free 

 from all impurities. The mineral has occurred also at the old 

 locality, east of Deerfield village, and appears in the State Col- 

 lection, Nos. 86, 87, labeled " Black Augite in Greenstone, 

 Deerfield." Also, opposite Turner's Falls a single perfect crys- 

 tal 4 mm long, black, with shade of brown, resting upon a botry- 

 oidal layer of diabantite in an amygdule. 



Chalcopyrite.— Occurs disseminated in particles in the 

 trap., in the prehnite, and in the caleite above, the latter rarely 



in minute, fre>h-looking>tnatcd tetmhedra in caleite. Also on 

 botryoidal diabantite and in the " chlorophocite " in Gill. 

 Sphale kite.— Earely in red-brown grains 5-6 mm long, fresh- 



looking and of- high luster in the interior, but generally 1 

 rounded by a bright red rust layer. In prehnite, epidote 

 alcite, and in the light gray diabase, filling cavities lined 1 



diabantite, with curious many-faceted globules. 



Pyrite appears in minute" fresh striated crystals in prehnite 

 and caleite and in limonite pseudomorphs in the same situation. 



