Z. V. Pirsson — Fowler ite variety of Rhodonite. 485 



on the other pinacoids and on all other faces it is almost 

 invariably lacking, even though in many cases the flat surface 

 of the planes and the sharp edges between them are quite well 

 preserved. In other examples the edges also are wanting, 

 causing a rounding off of the crystal, especially in the zones 

 001 a. 100 and 001 /\ 010. This rounding is also more noticeable 

 in the smaller individuals which are much more highly modi- 

 fied than the larger ones. 



All this made the crystallographic investigation of the 

 mineral a difficult matter and very accurate measurements an 

 impossibility. In examining a number of crystals, however, 

 some were found which gave reflections of the signal with a 

 fair degree of accuracy and from the best of these were chosen 

 the angles taken as fundamental. Some faces which had lost 

 their luster gave no reflections whatever, and not even an 

 approximate schimmer measurement could be made. The 

 planes being often well preserved however, the expedient of 

 giving them an extremely thin coating of a varnish of mucilage 

 and water was adopted and by this means using the d ocular 

 of Websky tolerably accurate measurements could be made 

 upon them, particularly upon the larger crystals. 



The following forms have been observed : 



a, 100, i-l 



fi, 401, 



—4-1 



e* 



, 441, 



-4' 



6, 010, i-l 



p* 201, 



2-1 



k, 



221, 



2' 



c,- 001, 



0* 401, 



4-1 



r, 



111, 



1 



TO, 110, I' 



q, 221, 



-2' 



n, 



221, 



2 



M, 110, / 













Of these planes e, p and <p are new. Also on some of the 

 smaller crystals the following new forms have been identified, 

 with only a fair degree of accuracy however, from causes 

 mentioned above: -§' 445; -f 883; -6', 661; on the 

 smallest crystals there are traces of macro- and brachy-pyra- 

 mids, which cannot be identified with even an approach to 

 accuracy. 



The angles taken as fundamental were 



001^100; 001 ^ 110; 100 ^110; 1 10 ^ 001 and 001 ^ 221. 



And from these we obtain the axial ratios and angles : 



a:6:c=l-078: 1: 0-62627; a=103° 39'; /? = 108° 48' 30"; 7=81055' 



The crystal form of the rhodonite from Pajsberg and Langban 

 has been investigated by G. Flink.* He has made some errors 

 in his calculations and correcting these, we have from his 

 measurements the following ratios and angles : 



d:&:c=l-0728: 1: -6217 ; a = 103° 18' 08", #=108° 44' 15", 7=81° 39' 16" 



which gives as close an agreement with the above as could be 



* Zeitschrift fur Kryst. 1886, pp. 506. 



