42 



It is a very soft (h=2'o) whitish green non-crystalliiie 

 mineral, having a conchoidal waxy fracture. It is translu- 

 cent in thin films but opaque in mass, and adherent to the 

 tongue. Its specific gravity is 2 '07. On exposure to air 

 it loses a portion of its combined water, and becomes of 

 a dead white colour and more opaque. The greenish tint is 

 due to the presence of small quantities of copper oxide 

 (I'll per cent). 



The following analyses show that this is a more highly 

 hydrated variety than most of the specimens of Halloysite 

 hitherto examined, and that it corresponds to the formula 

 AlA2Si02+5H,0. 



Analysis of Halloysite from Maidenpek : 



I. II. Meau. 



AlA 32-81 32-58 32-69 



SiOa 37-59 37-70 37-64 



H,0 28-59 28-27 28-43 



CuO 1-11 — 1-11 



100-10 — 99-87 



The calculated composition for the above formula is : 



AlA 32-86 



SiOa 38-37 



HaO 28-77 



100-00 

 A specimen of a similar mineral from the same locality 

 was found by Tietze to contain : 



AlA(Fe203) 25-20 



SiOa 44-96 



H,0 29-50 



99-66 

 Corresponding nearly with the formula AlaOsSSiOa + GHaO. 

 Showing a distinct difference in the relation of alumina to 

 silica from that existing in the specimen in question. 



