\ /.. Penffield- 'SpangoHte, a new copper mineral, 373 



In the above table we find ;i very satisfactory agreement be- 

 tween the measured and calculated angles from which we may 

 conclude that the measurement which we have accepted as 

 fundamental is very nearly correct. 



When all of the approximate measurements, which were ob- 

 tained from fifteen different zones measuring from the basal 

 plane above over the pyramids on the base below, are tabu- 

 lated ir is found that with few exceptions they fall into groups 

 indicating the existence of a series of pyramids, among which 

 we may Bafely assume the following, in addition to those winch 

 have already been mentioned: k, 2118, 1-2; n, *2TTc>, |-2 : r, 

 6538, 1-2; I, 6337, J-2; x, 6334, j-2; y, 211 1, 2-2; .:, 6332, 



The following table contains a summary of the measure- 

 ments which can be referred to the definite pyramids just men- 

 tioned. 



Table II. 





No of times 



Limiting 









obseryed. 



measurements. 



Average. 



Calculated 



c * k. 0001 a21T8 



3 



25° 48'-26° 7' 



25° 55' 



26° 41' 



c „ n. 0001 a 2ll6 



G 



33 54 -34 46 



34 26 



!!3 50 



c * o, 0001 a 2ll4 



19 



44 19-46 



45 3 



45 9 



c * r, 0001 ~ 6338 



3 



55 46 -56 53 



56 18 



56 27 



c a* /. 0001 ~ 6337 



5 



59 10 -60 33 



59 50 



59 53 



c * p, 0001 a 2112 



22 



63 12 -63 46 



63 30 



03 33£ 



c A sc, oooi ^ 6:;:;4 



6 



71 17 -72 30 



71 51 



71 39 



c - y, 0001 a2II1 



4 



76 48 -75 30 



76 13 



76 2 



c ^ & 0001 ^ 6332 



7 



79 17 -80 39 



80 4 



80 35 



An examination of the ahove table will inve an idea of the 

 frequency of occurrence of the different pyramids and the 

 accuracy of the determination. 



All of the measurements which have not already been given 

 in Tables I and II are collected together in the following table 

 where they are again arranged into groups, which indicate the 

 occurrence of vicinal faces agreeing nearly with simple forms. 





Table Til. 







Mean angle 



Limiting > 



o. of these 



Simple form to which 



on tin 1 bate. 



measurement. 



observed. 



they approximate. 



23° 





1 



2TI10. 1-2 



35 44' 



35° 30'-36° 



6 



n, 2ll6, £-2 



43 40 



43 15 -44 



5 



0, 2114, 1-2 



57 40 



57 26 -57 53' 



2 



r, 6338, 5-2 



61 37 



60 47 -62 41 



4 



p, 2ll2, 1-2 



2 



73 -73 5 



2 



x, 6334, |-2 



77 53 



77 5 -78 •",:; 



1 



y, 2TTl, 2-2 



88 15 





1 



a, 2110, /-2 



In all of the zones which were measured there was do indica- 

 tion of any hemihedral development of the pyramids. 



Cleavage. — The cleavage of spangolite is very perfect par- 

 allel to the base: thifl was a great help in studying the crystals, 

 as manv of the measurements recorded in Tables If and III, 



