﻿Vol. 66.] TOTJEMALINE-COEUNDUM KOCKS OP KINTA. 443 



(b) The Siputeh rock, in situ. — Specimens from this mass of rock vary 

 considerably. Some when collected were dead black and soiled the fingers, 

 and contained so large a quantity of metallic sulphides, precipitated no doubt by 

 the carbonaceous powder which gives the black colour, that oxidation of these 

 sulphides caused the specimens to crumble quickly away. 



In some slides the same bodies of tourmaline with corundum shells are seen 

 as in the Redhills rock. The larger cavities, however, are not common, 

 although numbers of them occur in boulders and pebbles hard by. 



In one case a round body was found to have a core of pyrite enclosing grains 

 of tourmaline. In another specimen a round body occurs, larger than usual. 

 The core consists of indigo-blue tourmaline ; the shell is of colourless corundum, 

 with a few grains of tourmaline and minute flakes of pale-brown mica. 



Arsenopyrite occurs, and in one slide it is shown to have been partly 

 replaced by micaceous material, leaving the original crystal outline sharply 

 defined. The arsenopyrite also encloses small flakes of the pale-brown mica, 

 which occurs too in the tourmaline base. 



Some specimens from this mass show yet another mineral that has not been 

 mentioned before. This is pleonaste, deep green in section, and occurring in 

 masses of small grains. The first slide cut containing this mineral did not show 

 any corundum, but a portion of the powdered rock afforded a considerable 

 quantity, some being blue. The tourmaline sometimes exhibits good basal 

 sections with crystal outline ; and a large part of the rock is composed of a 

 clear flaky mineral, which on separation proved to be white mica with a wide 

 axial angle, so wide indeed that some of the sections show an axis emerging 

 on a prism face. Another curious feature is that the lath-like sections 

 sometimes show a cross-fracture (secondary cleavage parallel to 010 ?). 



Another specimen shows tourmaline, spinel, wbite mica, brown mica, and 

 sulphides. 



Yet another variation is a tourmaline-hsematite rock, with a little white 

 mica. 



The tourmaline in the Siputeh rock is indigo blue. 



The following specimens were found as boulders or pebbles : — 



(c) A schistose and very dark rock, with small light bodies elongated along 

 the planes of schistosity and large solid bodies mainly composed of corundum. 

 The dark appearance of the rock was proved to be due to carbon. A little 

 corundum and tourmaline occur, also some pyrite. 



(d) In this there are traces of a fine base, which may be siliceous or 

 micaceous. Tourmaline and corundum occur. 



(e) Tourmaline is'abundant, and sometimes forms round bodies. Corundum 

 and minute flakes of white mica are subordinate. 



(/) The base of the rock is siliceous. Indigo-blue tourmaline and corundum 

 are abundant. There are some round bodies composed of tourmaline only. One 

 slide, containing some isotropic material, shows a pear-shaped body composed 

 of tourmaline, white mica, and granules that may be corundum (PI. XXXI, 

 fig. 1). Another slide shows a large cavity lined with corundum. 



(a) In this rock the tourmaline grains are larger than usual. There is a 

 little corundum and abundant pleonaste, with a quantity of white mica forming 

 a fine mosaic. 



(A) This is a compact rock consisting entirely of corundum, greenish-brown 

 tourmaline, and black dust. A separation of rock-powder was made and 9 per 

 cent of corundum obtained. In the slide the percentage of corundum appears 

 to be higher. (PI. XXXI, fig. 2.) 



(i) This rock occurs as angular blocks in stiff clay at Rotan Dahan. It 

 consists of corundum, tourmaline, and r utile. A similar rock has been 

 obtained from Pusing Lama. The rutile occurs in well-formed, deep-brown 

 crystals, and is present in some quantity. 



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