264 Prof. J. P. Cooke on the Vermiculites. 



Si. 



AL Fe. 



Fe. 



Mg. Ca. 



K. 



(1) 40-91 



17-19 11-03 



. . 



1904 030 



9-96 = 98-43 



(2) 40-91 



17-19 7-03 



4-00 



19-04 030 



9-96=98-43 



21-82 



830 211 



v. ■ 



•89 



7-62 009 



1-69 



21-82 



1041 





10-29 





2-12 



1-01 





1 





This new variety of vermiculite is so well marked, and the 

 composition so definite, that I have thought best to designate it 

 by the name Culsageeite. As regards its other characters, it has 

 a specific gravity of 2*225 (taken in alcohol), and about the 

 hardness of talc. Before the blowpipe the exfoliated mineral 

 fuses readily to a white enamel, but does not fuse in the flame 

 of a Bunsen lamp. 



To this variety of vermiculite belongs, as I have already inti- 

 mated, the original mineral from Millbury, analyzed by Crossley. 

 There can be no question as to the general accuracy of Crossley's 

 results ; and assuming that all the iron is in the ferric condition, 

 they give, as I have shown, almost precisely the atomic ratio 

 2:1:1:1. The only question that can arise is in regard to the 

 condition of the iron. I have therefore made an assay of the 

 iron by the accurate method I formerly described in the Amer. 

 Journ. Sci. vol. xliv. p. 347 (1867). One hundred parts of the 

 massive mineral gave 7*40 per cent, ferric oxide and 3-86 per 

 cent, ferrous oxide, which corresponds to a total of 10*56 ferrous 

 oxide. Crossley found 10*02 ferrous oxide ; but he separated 

 with great care the vermiculite from the steatite with which it is 

 mixed ; and this steatite was probably the source of the greater 

 part of the small quantity of ferrous oxide found in our assay, 

 which, though not made with pure material, shows conclusively 

 that the condition of the iron in the Millbury vermiculite is not 

 different from that in other varieties of the same family of mi- 

 nerals. 



Hallite. — Several years since^ this variety of vermiculite was 

 sent to me by Mr. John Hall, of Philadelphia, by whom it was 

 originally discovered, The examination then made showing that 

 the mineral was a new variety, if not a new species, of the ver- 

 miculite family, I gave to it the name of Hallite, in recognition 

 of the mineralogical services of Mr. Hall, who not only disco- 

 vered the mineral, but has carefully worked the locality and 

 observed the associations in which it is there found. A prelimi- 

 nary notice of the mineral under this name was published at the 

 time by Professor Leeds, of Hoboken ; but the interesting rela- 

 tions which the mineral bears to the subject of this paper have 

 made a further examination desirable. 



