200 Penfield and Howe — Chemical Composition 



JErom Ladu Mine, Sweden. 



V. Wingard. Material described as not quite pure and show- 

 ing traces of serpentinization, which accounts for the 

 high percentage of H 2 0. 

 VI. Hj. Sjogren. 



I. II. III. IV. v. VI. 



Sp.gr 3216 3-208 



SiO s 34-80 3549 35"43 35-55 35-26 35-13 



MgO 6008 54-28 56-29 52-86 55-48 55-16 



FeO 2-40 5-12 3"70 7*31 351 3-26 



CaO -20 MnO -41 



Alo0 3 '76 -. 



F 3-47 2-43 5-63 5-60 4-72 2-45 



H 2 1-48 1-37 3-07 2-16 



100-75 98-28 102-53 102-69 10204 98"57 



Oeq. toF 1-46 102 2-37 2'36 1-98 1-03 



99-29 97-26 100-16 100-33 10006 97-54 



Col. H 2 2-29 2-52 -85 



101-58 99-78 97-89 



It will be observed that these analyses show percentages of 

 Si0 2 varying from 84-80-35-55, agreeing with those made by 

 us in being higher than the corresponding percentages in 

 cliondrodite. The calcidated water represents the amount re- 

 quired to yield the ratio of RO : (F+OH) = 7 : 2. When 

 added to analysis II it makes the summation very satisfactory 

 but causes I to overrun. In the analyses of Wingard there 

 are already sufficient quantities of F and H 2 to give the re- 

 quired ratio. Sjogren's analysis is evidently too low. The 

 ratios are as follows : 



Si0 2 : KO : (F + OH) 



I. 0-580:1-535: = 2-65 : 7 : 



II. 0-592:1-428: = 2-90 : 7 : 



III. 0-591 : 1-458 : C-460 = 2-84 : 7 : 2-21 



IV. 0-593 : 1-422 : 0-447 = 2-92 : 7 : 2-20 

 V. 0-588 : 1-436 : 0-589 = 2-87 : 7 : (2-8?) 



VI. 0-586 : 1-430 : 0-369 = 2'87 : 7 : 1*8 



These ratios of Si0 2 : RO approximate closely to 3:7 as 

 required by our formula and in analyses III, IV and VI the 

 (F+OH) is not far from the correct ratio which should be 

 EO : (F + OH) = 7:2. Thus our formula for humite is also 

 substantiated by the analyses of other investigators. 



Clinohumite, {Humite Type III of Scacchi.) 



Of this rare mineral we have been able to examine two 

 specimens from Mte. Somma. For the first analysis the mate- 

 rial was derived from a specimen in the Brush collection, cata- 



