It) 



NEW YORK STATE MUSEUM 



figure 23. Certainly the occurrence of such similarity in crystal 

 habit involving one or more rare forms can not be set down as a 

 mere coincidence and when, as will be presently pointed out, the 

 geological conditions show a corresponding similarity at the two 

 localities, we are led to connect the two phenomena. 



At Andreasberg the pyramid Y was first noted by vom Rath 

 in 1867. Sansoni 1 in 1884 failed to find this pyramid, but as pointed 

 out by Cesaro, the doubtful scalenohedron (7.8.15.4) given by 

 Sansoni approaches very near the pyramid (8.8.16.3) m intercepts 

 and is probably the same. The latter compares the forms of the 

 Rhisnes calcites with those found by Sansoni at Andreasberg and 

 points out several interesting similarities. 



Both Rhisnes and Andreasberg lie in the horizon of the Devonic 

 and Upper Carbonic rocks and present the phase of subordinate 

 beds of limestone overlaid by graywacke, clay slate, silicious slate 

 and quartzite. In the vicinity of Andreasberg, these strata are 

 frequently broken through by granite masses 2 . These conditions 

 show a marked analogy to those existing at Union Springs, where 

 the limestone beds are overlaid by the shale and silicious slate of 

 the Marcellus and Hamilton groups and show evidences of con- 

 siderable local disturbance. The limestone on which the Union 

 Springs pyramidal calcite crystals are deposited is unique in that 

 the silicious residue obtained from its solution consists of minute 

 but perfectly formed quartz crystals. As pointed out by Pen- 

 field and Ford 3 pyramidal crystals of calcite, of the form (8.8.16.3) 

 and containing nearly 50% quartz sand, have been found in the 

 Bad Lands of South Dakota. It would, therefore, appear that in 

 at least two localities producing this rare pyramid as a crystal 

 habit, the occurrence is marked by the presence of silica under 

 rather unusual circumstances. When we add to this fact the 

 equally significant one that the formations at Union Springs and 

 at the Belgium and Hartz localities show in each instance dis- 

 turbed limestone beds overlaid by strata rich in silica we would 

 seem to have reason for connecting the pyramidal habit of calcite 

 with a crystallizing solution carrying silica in quantities approach- 

 ing saturation. 



CALCITE FROM HOWES CAVE 

 Calcite occurs at Howes Cave, Schoharie county, N. Y. in bril- 

 liant transparent crystals filling or partly filling the veins in the 

 Rondout limestone. The specimens which form the basis for the 



Sansoni. Att. Acc. Line. Mem. 3. 1884. 19:450. 



1 Phillips, J. A. & Louis, Henry. A Treatise on Ore Deposits. 1896. p. 384. 

 3 Penfield, S. L. & Ford, W. E. Silicious Calcites from the Bad Lands, Washington County. 

 S. D. Am. Jour. Sci. 1900. 9:352. j 



