116 Wells and Penfield — Herder He from Maine. 



angle 331^331 could not be measured with certainty as the 

 crystal, which was selected as best, gave double reflections from 

 one of the faces. The angle 102° 22' was selected as funda- 

 mental as it was from the brightest reflection, while 103° V 

 agrees better with the calculated angle of herderite. 



The resemblance between the two minerals is remarkable, 

 but since no chemical relation between them apparently exists, 

 except that both are phosphates, the similarity in form may be 

 accidental. 



The wliole specimen, except two or three small ciwstals, 

 was sacrificed for a chemical examination. The material was 

 so intimately mixed with albite that the greater part of it had 

 to be separated by Thoulet's solution. The specific gravity of 

 a pure crystal as shown by the heavy solution was 2 - 975, that 

 of the Stoneham herderite was 3-000. The material used for 

 analysis varied between 2-980 and 2 - 853. 



A careful qualitative analysis showed the presence of beryl- 

 lium oxide and the absence of all other bases except lime. 

 The phosphoric acid determination was made in a separate 

 portion by the molybdic acid method. The beryllium oxide 

 and water were determined by methods analogous to that 

 described by one of us for the analysis of herderite.* Unfor- 

 tunately the determination of lime was a failure and there was 

 not enough material for making a new determination. The 

 fluorine was determined by weighing silicon fluoride, using a 

 modification of Fresenius' apparatus. 



The results of the analysis are as follows : 



Found. 



P„0 6 40-81 



BeO 15-32 



CaOf [32-54] 



H 2 5-83 



F -40 



Insol 5-27 



Deducting 

 Insol. 



Calculated for 

 CaBeOHP0 4 . 



43-08 



44-10 



16-18 



15-53 



[34-35] 

 6-15 



34-78 

 5-59 



•42 















100-17 100-18 100-00 



The analysis shows the mineral to be a new and interesting 

 variety of herderite almost free from fluorine. The result con- 

 firms the idea advanced by Penfield and Harper that fluorine 

 and hydroxyl are mutually replaceable in herderite, and the 

 formula deduced by them for the mineral is confirmed. 



Sheffield Scientific School, March, 1892. 



* Penfield and Harper, this Journal, III, xxxii, 107. 

 f By difference. 



