CONTENTS. 
Chapteb XVII.— The Gondite Sevies— concluded. 
Chemical Composition of the Gondite Series 
Composition of gondite .... 
Composition of rhodonite-quartz- rock 
Alteration of the Gondite Series 
Evidence pointing to the formation of manganese 
ore by the alteration of spessartite and rhodo 
nite ....... 
The Mansar deposit .... 
Association of manganese-ore and spessartite 
Spessartite changes to manganese-ore . 
Alteration of rhodonite 
Time of alteration of the manganese-silicate-rocks 
into manganese-ores .... 
Hill deposits are dry .... 
Highest points of a gondite band consist of 
manganese-ore .... 
Manganese-ore deposits formed before the 
present topography 
Probably formed in Archaean times 
The way in which the manganese-silicate -rocks 
alter to manganese-ores 
The formation of braunite and psilomelane 
The ores are not porous 
The ores formed by combined replacement 
and decomposition of spessartite and 
rhodonite ...... 
Lack of examples showing solution of man- 
ganese ....... 
Carbon dioxide as the reagent producing 
alteration ...... 
Sulphuric acid as the reagent producing 
alteration ...... 
Alteration of rhodonite . . . . 
Carbon dioxide the more probable reagent . 
Rarity of open spaces in the altered rocks . 
Further reasons for supposing that alteration 
took place in Archaean times . 
Depths to which the manganese -ores extend 
Conclusions as to the Origin of the Gondite Series and 
the Associated Manganese-ores . . . . 
Paqe. 
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