444 Hillebrand and Merwin — Calciovolborthite (?) 



Analyses and Discussion. — In calculating the analytical 

 results shown on the preceding page there was deducted 30*6 

 per cent of matter insoluble in very dilute nitric acid in the case 

 of the yellow-green mineral, and 13*5 per cent in the other, 

 and calculating to 100. The original analytical summations 

 were 99*5 and 101 respectively. 



If C0 2 and Si0 2 are allowed for as normal carbonates and 

 metasilicates, an assumption not entirely in accord with the 

 facts, but the best that can be made, the molecular ratios 

 become : 



Yellow-green 

 Green-yellow 



,05 



: RO : 



H 2 total 



: H 2 0, 

 below 105' 



1 



3"73 



2-6 



2-03 



1 



4-37 



1-75 



1-42 



In view of the character of the material analyzed and the 

 doubt expressed a little above as to the homogeneity of one 

 of the samples, the above ratios do not permit us to decide that 

 the two minerals should receive different formulas. The differ- 

 ence is most marked in the water, but under the circumstances 

 this should not force a decision, especially since we know noth- 

 ing, in the first place, as to the function of the water — whether 

 truly water of crystallization or in its amount a function of atmos- 

 pheric humidity and temperature — nor, in the second place, 

 how much of it is to be assigned to contaminating minerals. 

 Until better material and better analyses are available we pre- 

 fer to regard the minerals as related to each other and of the 

 same type formula, the green derived from the yellow by par- 

 tial replacement of V 2 6 by As 2 5 and of CuO by CaO. 



When it comes to establishing the relationship of these min- 

 erals to others already known, difficulty arises also. Unques- 

 tionably the nearest known relative is calciovolborthite, for 

 which, on the basis of widely divergent analyses, Dana gives 

 the formula 4(Cu,0a)O.Y 2 O 5 .H 2 O. 



Optical data concerning calciovolborthite are entirely lack- 

 ing. We do not feel justified in making new species out of the 

 minerals herein described, but choose to refer them both for the 

 present to calciovolborthite, assigning that name to the yellow- 

 green variety and arsenical calciovolborthite to the greenish- 

 yellow derivative. 



The original belief of one of us (H.) as published by Mr. 

 Boutwell, that the arsenical variety is a new species, distinct 

 from the other, we do not care to press, although it may prove 

 to be so. 



As to the name calciovolborthite, it is difficult to see how it 

 ever came to be applied originally by Kammelsberg,* since the 



* The name Kalk-volborthit was not used by Credner, the first describer of 

 the mineral, as a statement in Dana's Mineralogy leads one to infer. 



