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The alteration of Pyrite by underground water

Published online by Cambridge University Press:  14 March 2018

John W. Evans
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Extract

It has for many years been proposed to form a reservoir with an area of some 36 square kilometres for irrigation purposes near Hiriyur in Northern Mysore, by erecting a dam at Marikanave, where the River Vedavati or Hagari crosses a rocky ridge running north-north-west and south-south-east.

Doubts were raised as to whether the rock would form a sufficiently firm foundation, but Mr. Robert Bruce Foote, late Superintendent of the Geological Survey of India, and my predecessor as State Geologist in Mysore, reported that it was in every way suitable for the purpose.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 12 , Issue 58 , November 1900 , pp. 371 - 377
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1900

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References

page 372 note 1 FeS2+H2O+4O2=FeSO4+H2SO4. A slight incrustation of hydrous aluminium sulphate was detected at one point by Mr. Holland. It is probable that sulphurous acid is at first formed, but is at once oxidised to sulphuric acid.

page 372 note 2 The action of carbonates'in promoting the formation of limonite from pyrite has been recognised by Dr. Justus Roth, Allgemneine and Ghemische Geologie, I, pp. 101-5, 236.

page 373 note 1 If the iron had been converted into hmmatite the volume would have been 69 to 65 cc.; if into magnetite 61 cc.; if into turgite 75 to 78; if into gSthite 80 to 88; while if it had passed into xanthosiderite it would have exceeded in volume the limonite. Accordingly, if all the iron be retained and none added, limonite is the only oxide or hydrate of iron that can form exact pseudomorphs after pyrite. It seems possible that the amount of space available may sometimes delermine the quantity of water which enters into combination with the ferric oxide.

page 373 note 2 Among mineral waters one analysis gives 13 litres. The highest in Thorpe's Dictionary of Applied Chemistry is 7.26 litres (III, p. 964).

page 373 note 3 The identity of the figures in the 4th and 7th columns is of course accidental.

page 375 note 1 Roth, loc cit. p. 236.