276 MANGANESE DEPOSITS OP INDIA : GEOLOGY. [PaRT II : 
Quite recently, Lindgrenl has made the following remarks on the 
formation of kaolin : — 
' The hydrothermal origin of large bodies of kaolin has been urged in several 
recent papers 2, by demonstrating the improbability of the formation of the 
mineral on a great scale by ordinary weathering and by indicating its connection 
with mineral deposits. Conceding this, it is nevertheless believed that kaolin is 
rarely formed by alkaline hot water at any considerable depth below the surface. 
Instances are multiplying (the occurrences at Cripple Creek among them) in which 
it can be shown that the kaolin of the upper levels exposed to oxidation changes 
into sericitic products in depth and that it is easily and abundantly formed by 
the action of solutions containing free sulphuric acid on sericitized metasomatic 
rocks and also, though less easily, on ordinary feldspathic rocks.' 
Again, as there is no evidence that the felspathic rocks of the kodur- 
ite series of Vizagapatam have ever passed through the sericitic stage, 
there is no necessity to consider sulphuric acid as the reagent to which 
their chemical alteration is due ; but rather water containing carbon 
dioxide, reinforced by the addition of potassium carbonate as soon as 
some of the orthoclase had been decomposed by the attacking waters. 
From the foregoing extracts it will be seen that opinions differ as to 
the amount of carbon dioxide present in the 
' ■ solutions producing kaolinization ; but that it is 
agreed that kaolin is formed near to the surface rather than at consider- 
able depths, and that, according to Lindgren, it occurs in the zone of 
oxidation, giving way to sericite at greater depths. 
Now let us deal with oxidation. C. R. Van Hise 3 has divided the 
outer crust of the earth into three zones : an upper zone of fracture, a 
nr. tt t lower zone of flowage, and a middle zone of com- 
ine zone oi iracture _ ' 
and belt of weather- bined fracture and flowage.4 The zone of fracture is 
that near the surface, and probably continues to a 
depth of about 3,000 feet. This upper zone of fracture is divided by 
Van Hise 5 into : — 
'( 1 ) an upper belt of weathering, and (2) a lower belt of cementation. The 
belt of weathering extends from the surface to the level of ground-water, and for 
1 "The Relation of Ore-deposition to Physical Conditions,' Economic Geology, II, p. 
120.(1907). 
2 Stutzer. Zeitschrift fiir frakt. Ocologu, XIII, pp. 333-336. (1905). 
3 ' Some Principles Controlling the Deposition of Ores', Trans. Amer. Inst. Min. 
Eng., XXX, p. 30, (1900). 
* Van Hise elsewhere considers that the zones of fracture and flowage — diWsions 
of the earth's crust bastd on structural considernlions — correspond respectively to the 
zones of katair.orphism and anaiiiorj)hism — divisions of the earth's crust from the 
metamorphic point of view. See ' A Treatise on Metamorphism', U. S- Geological 
Survey. Monograph XLVII. p. 190, (1904).' 
5 'Some Principles Controlling the Deposition of Ores', Trans. Amer. Inst. Min. 
Eng., XXX, p. 72, (1900). 
