llld SERPENTINE OF MONTVILLE, NEW JERSEY. 



constant relationship in thickness between the serpentine and the nu- 

 cleus, the coating varying from the fraction of one to several inches 

 (rarely more than 5 or G) in thickness. Figs. 1, 2, and 3, PI. xxxi, are 

 characteristic forms, the nodule shown in fig. 1 having been broken 

 13 to leave the nucleus entire, while figs. 2 and 3 are from speci- 

 mens cut through the renter and polished. In fig. 1 the nucleus is 

 about 1 1 inches long and 5 inches wide by 2 inches thick iu its greatest 

 dimensions, tapering down to a blunt point at the left. Larger were 

 fouud, and others iu which the nucleus had completely disappeared. 

 Nol the least interesting featureof thecase was the discovery that these 

 nuclei varied in color, some being gray, slightly greenish, otheis pure 

 white, and that each had a coating of serpentine characteristic of itself. 

 That surrounding the gray nuclei is deep, bright green, sometimes 

 almost black, and scarcely translucent ; that surrounding the white nu- 

 clei, on the other hand, is of a beautiful light oil yellow, almost amber 

 color, and translucent almost to transparency. The two varieties are 

 in most cases distinct, rarely, so far as observed, grading into one an- 

 other. Both varieties show at times narrow veins of amianthus or 

 chrysotile, though these are most abundant in the light colored variety. 

 On exposure to weather, alter quarrying, a shrinkage takes place, so 

 that in most cases rhe serpentinous crust shells off only too readily, in 

 small fragments, and often almost as clean as the burr front a chestnut, 

 leaving the nucleus compact and fresh, with a firm, smooth and shining 

 surface, and with only thin patches of serpentine adhering here and 

 there, as in fig. 1 of plate. 



On examination with a pocket lens it becomes apparent that the 

 connection between the serpentine coating and the nuclei is much 

 closer than at first appears, the mineral of the nuclei near the point of 

 contact assuming a faint yellowish or greenish tint. Small veins and 

 tongues of serpentinous matter also in places project into the uuclei, 

 shown in figs, i! and 3 of plate, where the light gray mineral of the 

 nucleus shows up in strong contrast with the dark serpentine. Thin 

 sections cut so as to include portions of both serpentine and nucleus 

 show the latter to consist of a granular aggregate of short and stout 

 crystals of all sizes up to 2 mm in diameter, colorless or slightly gray, 

 and no'nph-ochroic though polarizing brilliantly in yellow, green, and 

 violet colors. The mineral is monocliuic in crystallization, gives ei 

 tinction angles on sections approximately parallel to the clinopinacoid, 

 varying from L'7 to 36°, ami shows the optic axes in the plane of sym- 

 metry. Well-defined prismatic cleavages are developed, which, as seen 

 iu basal sections, ••ut one another at nearly right angles. A third cleav- 

 parallel to the orthopinacoid was observed in a few instances. 

 Polysynthetic twining is common; twin lamelhe, as shown in basal 

 sections lying parallel with the orthopinacoid. All the above charac- 

 teristics arc indicative of diopside. These indications are confirmed 

 by the analyses to he uoted later. Examination of portions of the sec- 



