- The Deerjield I>ijk> >nn/ if* Minerals. 351 



broad, flattened 

 trap. 



ehlorophoeite, and calcite. 



Quartz.— Only in a single specimen from the Cheapside 

 veins did quartz occur associated with the zeolitic mineral* 

 Here a few minute, elongated prisms appear in and on preh- 

 nite. Toward the upper surface of the dyke occur veins 

 4-o cm wide, coarse eomby quartz whose terminations interlace 

 insularly at the center. Between the wall on one side and 

 the regular cockscomb quartz a layer 10 mm thick of broken-up 

 quartz crystals, re-cemented by quartz, showing that the vein 

 tad once partly filled itself and then by the rubbing together 

 of the walls the work was interrupted. In other parts of the 

 vein the quartz is much gashed by broad, thin cavities which 

 are often as many as twelve, one above the other, and parallel 

 to the walls as well as scattered in various directions. They 

 seem to have been produced by the repeated formation of a 

 layer of some mineral, now wholly gone, probably selenite or 

 barite. Quartz occurs more abundantly in the veins cast of 

 Deerfield than at Cheapside in form of amethyst, agate, Canad- 

 ian and calcedony, as mentioned by President Hitchcock, and 



Selenit* «a that selenite had 



been found in the DeerBeld trap by Professor Silliman (this 

 Jour., vol. v, p. 212), and described moulds of unknown crvs- 

 r /'•< left in the quartz of the zeolitic veins east of Deertield. 

 Casts taken from these moulds show that the mineral which 

 * disappeared was selenite which < ., eurred here verv abund- 

 ^'tl.v and in web-formed crystals 20 mm long. The quartz rises 

 mto the moulds in sharp parallel crests where it had penetra- 

 ted between the laminas of the selenite along the perfect cleav- 

 age. 



In the Cheapside veins similar, but smaller negative crystals 

 occur in the prelmite which at times rose around and covered 

 the selenite, before its disappearance, forming thus rude pseu- 

 domorphs; and 1 suspect that part, or all of the abundant 

 the prehnite, quartz and datolite may be due to this 

 mineral. 



Fluorite.— Emerald -green dodecahedra-like beads strung 

 Upon a satin thread occur half imbedded in and scattered over 

 and among the last-formed fibrous prehnite, the crystals -03 mm in 

 length, also in the same relation to epidote and enclosed in the 

 calcite which succeeds these. In a single case each, emerald- 

 green octahedra and cubo-octahedra, •03 mI0 in size, in a drusy 

 cavity in epidote, and in green cubes upon prehnite. 



