of Chondr oolite, Humite and Clinohumite. 199 



Second Analysis. 

 I. II. Average. Ratio. 



Si0 2 36-84 36-63 



MgO 56-21 56-42 uu o± 



FeO 2-22 2-21 



F._ 3-89 4-02 



H.O 2-18 2-08 



36-74 



•612 



56-31 



1-408 



2-22 



•029 



3-96 



•208 



2-13-4-9 



•236 



101-36 





: 1-66 





Oxygen equivalent to F 



99-70 



These analyses differ from those of chondrodite in being 

 about 3 per cent higher in silica and also the ratios are dif- 

 ferent as shown by the following : 





Si0 2 



(MgO + FeO) 



(F + OH) 



1st Analysis, 



0-6105 



: 1-444 



0-423 = 2-97 : 7 : 2-05 



2d Analysis, 



0-612 



1-437 



0-444 = 2-99 : 7 : 2-16 



These ratios approximate closely to 3 : 1 : 2, indicating that 

 the formula of humite is Mg 6 [Mg(F . OH)] s [Si0 4 ] . The ratio 

 of F : OH in the first analysis is nearly 2 : 3 and in the second 

 about 1 : 1. We give beyond the theoretical composition for 

 both ratios, together with the analyses in which the FeO has 

 been calculated as MgO and the total brought to 100 per cent. 





Theory where 





Theory where 



First analysis. 



F:OH= 2:3. 



Second analysis. 



F: OH =1:1. 



Si0 2 37-15 



37-53 



37-24 



37-50 



MgO _ 58-56 



58-38 



58-27 



58-34 



F 3-12 



3-17 



4-02 



3-96 



H 2 : 2-48 



2-25 



2-16 



1-87 



101-31 



101-33 



101-69 



101-67 



O eq. toF_. 1-31 



1-33 



1-69 



1-67 



These analyses show a very satisfactory agreement with the 

 theory and we may regard the formula of humite as well 

 established. 



Previous analyses of humite. — The following analyses are 

 available for comparison. 



From Mte. Somma. 



I. Rammelsberg. Grayish yellow crystals. 

 II. G. vom Rath. Light brown crystals. Mean of two 

 analyses. 



III. Wingard. Light yellow crystals. Mean of two analyses. 



IV. Wingard. Dark yellow crystals. 



