BrusA and Dana — Mineral Locality at Branchville. lM.~> 



remove all question as to whether the results gave the true 

 oompositioD <»t" the mineral, a second and independent analysis 

 was made For this the very best material was selected and 

 after being separated was minutely examined microscopically 

 to make sure of ir> purity. The results as will be seen are 

 identical with those of the first. 



The two samples were picked from separate specimens and 

 the material was apparently very pure. Unusual care was 

 taken in picking the second sample and its purity is indicated 

 by the small amount of quartz present. 



The formula indicated by both the analyses is 3RO . P 9 0, t 

 JH.O or R,(PO 4 ),+iH i where K = Mn, Fe, Ca, Xa,, K and 

 Li,. There is no simple ratio between the alkalies and the 

 remaining bases. The results vary considerably from those of 

 Pentield in his original analysis. This is undoubtedly due to 

 the fact that the present material was much purer than that 

 analyzed by him. Pentield found about 1-i per cent Ca(), 

 (probably due to admixed fairtieldite) only about 6 per cent of 

 alkalies and 8->7 per cent of H 2 0. The formula which he 

 arrived at, however, is confirmed except in the amount of H 2 0. 

 It will be seen that the composition now established is essen- 

 tially the same with that deduced for fillowite on the basis of 

 Pentield's original analysis. 



Fillowite. 



The fact just stated, that our former formula for fillowite is 

 the same as that now obtained for dickinsonite, has made us 

 very anxious to prove that our early results were trustworthy, 

 especially since the material in hand at the time of our first 

 investigation was very scanty. Unfortunately, among the large 

 number of specimens recently obtained from Branchville, we 

 have not succeeded in finding a trace of this mineral. We have 

 been forced consequently to revert to the few original specimens 

 still in hand. The best of these we gave to Mr. Wells, and 

 from it he picked out about O'To gram, in the homogeneity of 

 which he had entire confidence. A new analysis of this has 

 been made by him with the following results; for comparison 

 we quote the original analysis by Pentield. 



Ratio. Analysis (1878) Penfleld. 



PoO, 39-68 -=- 142 = *279 1- 39-10 



FeO 9-69 -r- 72 = -135 ") 9-33 



MuO 39 58-t- 71 = 557 j 39*42 



CaO 3'63 -=- 56 = 005 y -847 3'04 4*08 



Xa,0 5 44 -r- G2 = -088 5 71 



Li,0 007 -f- 30 = -002 j 0-06 



B,0 L'58 -*- 18 = -088 0"31 166 



Quartz 1*02 0*88 



10069 100-27 



Am. Joint. Sot. — Third Series. Vol. XXXIX, No. 231. — March, 1890. 

 15 



