Crystallization of Parisite. 535 



Crystallography. — Crystallographic data concerning pari- 

 site are but scanty, and for that reason a rather full account of 

 our observations on the Quincy crystals is here presented. 



Parisite was determined to be hexagonal by Des Cloizeaux* 

 in 1874, and he found on the type crystals from Muso valley 

 series of pyramids of both orders, the base and a prism. The 

 value of 6 calculated from his measurements was 3*2891. His 

 crystals were doubtless the large and rather rough ones first 

 found there and he describes them as badly striated. He sug- 

 gests a rhombohedral interpretation of the crystals, but with 

 no reason for its adoption. 



Vrbaf in 1888 measured three crystals from Muso valley 

 which gave good readings for the form o from which he calcu- 

 lated the element c = 3'3646. 



Penfield and Warren;}; in 1899 described a new occurrence 

 of parisite from Montana, but the crystals were too badly stri- 

 ated to give reliable measurements. 



Cesaro,§ in 1907, gave the results of measuring minute but 

 brilliant crystals of parisite attached to quartz. The locality 

 is Muso, but apparently from a deposit different from that 

 which yielded the original crystals. He derives the value 

 c = 3 - 405, but makes no statement as to the number of crystals 

 or faces measured. His crystals showed distinct rhombohedral 

 development and Cesaro adopts a rhombohedral position with 

 the pyramid f (1124) as the positive unit suggesting, however, 

 a possible preference for the choice as unit of the steeper pyr- 

 amid g (1123). The latter choice was independently arrived at 

 by the study of the much more complex crystals of parisite 

 from Quincy as shown below. 



Tschernik| found on crystals from Mukden, Manchuria 

 forms and habit very like those of Montana crystals. 



The crystallographic data of these papers is collected in the 

 following table which shows the forms previously found on 

 parisite. Discussion of the relation of synchisite to parisite 

 will be found on a later page. 



The parisite crystals found at Quincy are, on the whole, 

 favorable to crystallographic study. They are mostly small ; 

 1 to 3 mm in length, with a maximum of about 2 cm and for the 

 most part very slender. Many hundreds of these tiny crystals 

 and crystal fragments were found in the sand-like debris left 

 after washing the large collection of specimens of pegma- 

 tite ; many crystals are also visible, of course, still attached to 

 the matrix. The crystals vary enormously in habit and quality 



* Min. ii, 162, 1874. + Zs. Kr., xv, 210, 1888. 



\ This Journal, viii, 21, 1899. § Bull. Ac. Belg., 321, 1907. 



I Vetar. Min. Ges. St. Petersb., xliv, 507-545, 1906, Abstract in N. Jahr. 

 Min., 1909, ii. 





