318 Penfield and Sperry — Miner alogical Notes. 



where it was broken off, is covered with crystalline facets very 

 irregularly distributed, so that the system of crystallization can 

 not readily be told. The most prominent face on the specimen 

 is a prismatic face m measuring nearly one square inch in sur- 

 face, but with irregular contour and deeply pitted by crystalline 

 depressions scattered irregularly over its surface. At either end 

 of this face and for a distance of one half an inch back, the crys- 

 tal is terminated by a series of dihexagonal pyramids, or beryl- 

 loids, in parallel position, there being six of them at one end 

 and four at the other ; these run into one another in a 

 most confusing manner, while most of the specimen is covered 

 with such a multitude of berylloid and prismatic faces, that 

 their relation to each other can only be made out with diffi- 

 culty, which is further increased by the somewhat curved and 

 dull nature of the faces, so that they give only poor reflections 

 on the goniometer. The forms which were identified are as 

 follows : 



m, 1010, / 



a, 1120, i-2 



p, 1011, 1 

 v, 2131, 3- 



k, 4261, 64 

 n, 3141, 44 



f. 3361, 6-2 



Of these, n and jp were identified only once. The common 

 berylloid at the ends of the prism is v with the points rounded 

 off as if they had been dissolved away. Where 

 the berylloids join the prism, the steeper k 

 faces are common. Fig. 1 represents the ar- 

 rangement of these faces in a single ideal crys- 

 tal, while the specimen in hand might be con- 

 sidered as an aggregate of such crystals, with 

 prismatic faces in common terminated by a 

 series of berylloid points. The whole mass has 

 a very much eaten out or etched appearance, 

 and the idea suggests itself that this unusual 

 and curious development, so unlike our ordi- 

 nary Connecticut beryl, has perhaps resulted 

 from the action of some solvent upon a large 

 mass of beryl. Although the angles obtained 

 in measuring the faces are only approximate, the 

 best of them agree closely with those calculated from Kokscha- 

 row's fundamental measurements,* while the determination was 

 further facilitated by the occurrence of the faces in zones. 

 The following angles were measured, and are given in the 

 table, along with the calculated values, the number of times 

 that different faces were measured and the limiting values. 



* Materialien zur Mineralogie Russlands, i, 147. 



