A CRITICAL DISCUSSION OF THE CRYSTAL -FORMS OF 



CALCITE. 



By H. P. Whitlock. 

 Presented April 14, 1915. Received, January 3, 1915. 



The enormous mass of crystallographic data which have been 

 furnished by investigators of the species calcite since the time of 

 Zippe and Haidinger has resulted in the addition of many new forms 

 to the list available to those critical monographers. Whereas the list 

 of Irby, published in 1878, recognized 156 well established forms, a 

 similar list brought up to date will contain more than twice that 

 number. Faced with this multiplicity of forms, thickly studding the 

 field of gnomonic projection, the modern crystallographic investi- 

 gator of calcite is ordinarily at a loss to distinguish the common 

 forms from the less common and these again from the rare or unusual 

 ones. It is the purpose of the present paper to furnish a criterion by 

 which the probability of occurrence may be determined for any form, 

 and by an extension of the critical methods, new forms tested. 



In the following discussion the method of developing normal 

 series proposed by Dr. Goldschmidt 1 has been adopted as a primary 

 basis of comparison. A brief exposition of Goldschmidt's method of 

 developing normal series is here appended with the object of render- 

 ing the analysis more intelligible to the reader. 2 



The mechanical basis of the method of normal series is to be found 

 in the preliminary hypothesis that every face is crystallonomically 

 possible which is perpendicular to a direction of particle attraction. 

 In this way a possible crystal face may be assumed perpendicular 

 to the resultant of any two directions of particle attraction, which is 

 equivalent to saying that every crystal edge may be replaced by a 

 possible crystal face. But, in as much as each mechanical resolution 

 or redivision of the crystallizing forces is accompanied by a weaker 



1 Goldschmidt, V., Zeit. f. Kryst., 28, 1 and 414 (1897), 



2 For a short summary of Goldschmidt's article see A. J. Moses, School of 

 Mines Quarterly, 25, 415 (1904). 



