86 



Cincinnati Society of Natural History. 



are associated. The largest of these needles occur in the 

 quartz where they are not only in close proximity to un- 

 doubted epidote, but here they can also be seen to be projec- 

 tions from epidote grains. These larger needles are traceable 

 into those of smaller and smaller dimensions, until they seem 

 even to merge into the hair-like inclusions represented in 

 Fig. i. The fact that, occasionally, a somewhat inclined 

 extinction is observed in these needles is better in accord with 

 a monoclinic rather than a tetragonal system of classification. 

 That these needles should occur as a hexagonal network in 

 the mica, though not before noticed, need excite no surprise. 

 It is well known that mica often exerts an orienting effect 

 upon acicular crystals included in it, even when these are of 

 secondary origin. Hollrung,* for instance, figures and 

 describes similar crystal needles in rubellan, where they 

 also intersect at angles of sixty degrees. These, he is inclined 

 to believe, are rutile. LacroixT also described as rutile those 

 minute needles which cause the asterism of the Canadian 

 phologopite. Brush \ describes inclusions of magnetite, with 

 hexagonal arrangement in the mica of Pennsbury, Penn. 



Such hexagonally-arranged inclusions in mica usually follow 

 the direction of pressure lines (Ger. druckfiguren), which are 

 probably also solution planes of this species in sense in which 

 this term is used by Judd. An attempt was made to decide 

 whether this was also the arrangement in the present case, 

 but the results were not conclusive, because of great difficulty 

 in securing good pressure figures in the minute scales of 

 mica, where these hexagonally-arranged needles were visible. 

 An occasional hexagonal-arrangement in the other minerals 

 than mica, while at first thought indicating the influence of 

 the needles themselves, is probably rather to be accounted 

 for by the influence of mica, which has disappeared in the 

 preparation of the section. 



While, therefore, these needles bear a certain resemblance 

 to others, which are usually interpreted as rutile, the weight 

 of evidence, in the present case, seems to point strongly to 



* Untersuchungen uber den Rubellan, Tscher. Min. Mitth. V, pp. 3 J 5-3 lS ' 

 Plate III, 1883. 



t Bull, de la Soc. Min. de France, Vol. VIII, p. 99, 1885. 

 J Amer. Jour. Science [3 . Vol. XLVIII. p. 361, 1869. 



