Dec. 1861.] Geology of the Neilyherries. 245 



Lustre. — Some of the scales possess the lustre of the adamant 

 when the light falls upon them. 



Nearly all reflect objects passing in front. 



In the middle of some of the blocks nodules of the same ore oc- 

 cur in a decomposing state. 



In the lighter variety almandines of inconsiderable dimensions 

 are occasionally embedded. 



Pisiform iron ore is found in many of the banks about the Can- 

 tonment, under the vegetable soil, in rounded grains from the size 

 of a pea to a pin's head, 



This mineral is an oxide of iron. Yields water in the mattrass. 

 Its dust is taken up by the magnet. 



Structure amorphous though some of the grains peel in concen- 

 tric coats. 



This ore is distinct from the radiated pea iron ore, which the 

 roads are made of at Madras, and which I believe is called late- 

 rite, a vague term, not found in any works on mineralogy, and 

 made use of to denote any outlying iron whose mineralogical place 

 is undetermined. 



Many of the detached masses of decomposing rock into the com- 

 position of which iron largely entered are wholly encrusted with a 

 mamillary coat of oxide of iron. The iron of the rock probably 

 decomposing the water in the air that came in contact with its 

 surface, separated its elements, liberating the hydrogen, and com- 

 bining with the oxygen. 



Amidst the heaps of red haematite on the side of Dodabett, I 

 met- with blocks of sand stone traversed by thread veins of iron. 



This stone fractures into doubly oblique prisms, the longer side 

 being parallel to the metallic veins. It is quite adventitious I 

 suspect, and is a compact granite altered by the metal that has 

 traversed it. 



Iron earths of red and brown colors occur in the same locality. 



The blocks of haematite are intersected by veins of crystalline 

 rose, prase, yellow and amethystine quarts, embedding carbun- 

 cles. The assays of the foregoing irons are not yet completed. 



