

202 HOLLAND: SIVAMALAI SERIES. 



black spinelloids, besides tabular six-sided crystals of corundum^ 

 larger than any of the other constituents and sometimes measuring 

 half an inch across. The corundum is very irregular in its distri- 

 bution through these rocks. 



Near the western end of the row of small hillocks very coarse- 

 grained, pink felspar-veins occur, carrying crystals of corundum 

 measuring sometimes over six inches across. In this rock several 

 other accessory minerals occur, like biotite, muscovite, deep*blue 

 apatite, zircon, zinc-spinel (automolite) and a sulphur-yellow platy 

 form of chrysoberyl 1 (BeO. Al<j0 3 ). The felspar is a complicated 

 intergrowth of more than one species in which a well twinned albite 

 and orthoclase are prominent forms. 



The felspars are too intimately intergrown to permit of separa- 

 tion for independent examination, but chemical analysis of a frag- 

 ment having a specific gravity of 2*594 shows that the felspar con- 

 sists of a mixture of orthoclase with almost pure albite. Micro- 

 scopic examination shows the development of a small amount of 

 muscovite and kaolin in the felspars, in consequence of which the 

 silica is a little lower and the alumina a little higher than they other- 

 wise would be in this analysis. 



Analysis of Jragment of No. 11,465, consisting of intergrown 

 orthoclase and albite •, with a small quantity of secondary Mus- 

 covite and kaolin. 



Sp. Gr. 



of 



piece analysed 



2594 





Silica 

 Alumina 

 Ferric oxide 



• 

 • 

 • 



• • * 



• • • 



> • 

 • 

 • 



63*26 



21 87 



0'22 



Lime • 

 Potash . . 

 Soda • 

 Loss on ignition 



• • • 



• • 



• • * 



• • 



• • 



• • 



• 



0'2I 



3-09 



I0'25 



078 











99-68 



On adjusting to 100, neglecting the loss on ignition, due probably 



1 Determined by Mr. L. Fletcher, F.R.S. 

 ( 34 ) 



