211 ON A NEW VARIETY OF HALLOYSITE FROM SERVIA. 



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 * 1 1 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 

 Al z 3 2SiO a + 5H a O. 



Analysis of Halloysite from Maidenpek : — 



I. II. Mean. 



A1 2 3 3*-8i 3 2 *58 3 2 ' 6 9 



Si0 2 37-59 377o 37"64 



H 2 28-59 28-27 28 '43 



CuO i'ii — i'ii 



iocrio . — 99*87 



The calculated composition for the above formula is : — 



A1 2 3 32-86 



Si0 2 38-37 



H 2 2877 



IOO'OO 



A specimen of a similar mineral from the same locality 

 was found by Tietze to contain : — 



Al 2 3 (Fe 2 3 ) 25-20 



Si0 2 44'9 6 



H 2 2950 



99-66 



Corresponding nearlywith the formula Al 2 Oj3SiO z H-6H 2 0. 

 Showing a distinct difference in the relation of alumina to 

 silica from that existing in the specimen in question. 



