New York State Education/Department/^/,/^ : ;/ 



New York State Museum 



JOHN M. CLARKE Director 



Bulletin 98 

 MINERALOGY 4 



CONTRIBUTIONS FROM THE MINERALOGIC 

 LABORATORY 



BY 



H. P. WHITLOCK 

 MINERALS FROM RONDOUT, ULSTER CO. 



In the spring and fall of 1904, the New York State Museum came 

 into possession, through purchase and by the gift of Mr P. E. 

 Clark, ot a very complete and representative collection of minerals 

 from the mines of the Newark Cement Co., at Rondout. As 

 such a mass of mineralogic material from this interesting local- 

 ity has probably never before been available for study, the 

 writer has availed himself of this opportunity to contribute these 

 brief notes in the hope that they may prove of value in furthering 

 a detailed knowledge of the mineral occurrences of New York. 

 The writer wishes to express his thanks to Mr Clark for the many 

 courtesies extended to him in his work. 



General description. The mineral material consists princi- 

 pally of the filling of seams or veins in the Rondout limestone 

 which constitutes the cement rock of these deposits. Of these 

 vein minerals calcite predominates and is characterized by a wide 

 and interesting variation in crystal habit. Crystallized quartz 

 and dolomite occur associated with the calcite together with pyrite 

 and marcasite of a younger generation. All of these present 

 characters of interest and will be described in detail. 



Marcasite. Marcasite occurs implanted on the calcite and 

 quartz of the vein filling and less frequently impregnating the cal- 

 cite in minute detached crystals. The crystals vary from 5mm 

 in width, parallel to the b axis, to microscopic individuals. In 

 crystal habit they present the usual types, the combination shown 

 in figure i representing the prevailing habit. The faces are in 

 general marred and distorted by striations and vicinal planes to 

 such an extent that exact goniometrical measurements were 



oFigures 1 and 2 are shown with the 6 axis vertical. 



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