﻿Vol. 66.] TOURMALINE-CORUNDUM ROCKS OF KINTA. 439 



Angular masses of tourmaline-corundum rock are often to be 

 seen embedded in the decomposed schists above the limestone ; but 

 I have never seen a continuous band of such masses, nor is this 

 surprising when one considers how great is the effect of weathering 

 in this country. In the month of August 1909 huge masses of the 

 rock could be seen in softened schists, in an excellent section in 

 the Pusing Bharu mine. 



On rising ground boulders of the tourmaline -corundum rocks 

 are sometimes very numerous and practically in situ. On one 

 ridge, the left bank of the Eiver Mendrus, I found that the soil 

 even is formed from these rocks, containing large quantities of 

 colourless and blue corundum and tourmaline. 



The two best occurrences, however, of the tourmaline-corundum 

 rock in situ are on the Redhills Mining Company's property, and 

 about half a mile out of Siputeh on the bridle-path going towards 

 Batu Gajah. On the Redhills property the rock is associated with 

 iron-stained schists, and strikes about due north and south. At 

 the southern end of the outcrop, near the Pusing Lama Company's 

 boundary, it stands out much like a dyke from the surrounding 

 country, owing no doubt to its superior hardness and resistance 

 to weathering. 



On the bridle-path near Siputeh an enormous mass of the rock 

 occurs. The surface is much iron-stained, and it was necessary 

 to have recourse to blasting before good specimens could be 

 collected. It was possible then to see traces of the original 

 bedding, and it was found that in parts the rock was rich in 

 carbon and heavily mineralized with metallic sulphides, chiefly 

 arsenopyrite. No gold or silver was found on assay, however 

 nor was any tin-ore found. 



Tin-ore frequently occurs in schists with which the tourmaline- 

 corundum rocks are associated, but I have never yet found any 

 cassiterite in the tourmaline-corundum rocks themselves. 



Apart from the occurrences of these rocks in situ, the alluvium 

 overlying the limestone is rich in pebbles and boulders that afford 

 excellent material for study, and in some places the surface of 

 the limestone is so strewn with them that one cannot escape the 

 conclusion that they are all that remain of a former cap of younger 

 rocks. The description below is largely based on such material. 



So far, I have spoken generally of ' tourmaliue-corundum rocks.' 

 In composition, however, they vary considerably, but I have found 

 that it is possible to explain this difference as being due to greater 

 or less alteration ; indeed, it is possible to trace a gradation 

 from light- coloured specimens with little or no tourmaline or 

 corundum to a rock composed of tourmaline, corundum, and black 

 carbonaceous dust, or to a rock composed of corundum and white 

 mica. The clearest method of describing in detail the various 

 rocks (including the schists) will be to arrange representative 

 specimens under headings, beginning with the least altered. The 

 most abundant rock, apart from the schists, and therefore the 

 rock that should be considered as the type of the group, is 

 the Redhills rock, which will be described in its place. 



