Vol. 68.] THE GOPENG BEDS OF KIXTA. 145 



(3) The Mesozoic Granite. 



The border of the Mesozoic granite is generally marked by soft 

 granitic rocks rich in kaolin and tourmaline, and carrying tin-ore. 

 The typical granite is coarsely crystalline, with large porphyritic 

 crystals of orthoclase. The fact that it is intrusive into the lime- 

 stone, the Gopeng Beds, and the phyllites and quartzites, is proved 

 by numerous sections. 



Modifications of the Mesozoic granite, such as are commonly 

 found in tin-bearing areas, are found in the vicinity of Gopeng 

 also, but need not be described here. 



(4) The Gopeng Beds. 



These beds, as already stated, resemble glacial clays, or till, and 

 boulder-clay. They have been examined, not only in the excellent 

 sections afi'orded by the hydraulic operations on the land leased to 

 the Gopeng Mining Company, the New Gopeng Mining Company, 

 and the Kinta Tin-Mines Ltd., but also by means of bores which 

 were put down to prove if possible, among other points, that 

 the limestone lay beneath them. 



The clays are generally pale in colour, a light grey or even 

 white being the usual hue ; but, near the surface, they are fre- 

 quently stained red by the deposition of iron hydroxide, which also 

 produces a curious mottled appearance, the reason for which has not 

 been determined. Also in the vicinity of certain intrusive veins 

 from the Mesozoic granite, and along the junction with the main 

 granite mass, the clays are stained deep red, but not invariably. 



The boulder-clays are of the same colour as the clays, and undergo 

 the same staining. 



For the most part a fairly distinct bedding of the clays and 

 boulder-clays can be observed, and in some sections the separation 

 of individual beds is clear ; but, on the other hand, it may be 

 difficult in some places to find any trace of bedding at all. It is in 

 the best sections showing stratification that one sees to how great 

 an extent the beds have been faulted, and how irregular is the 

 degree of dip. In some cases sections have been exposed, showing 

 finely-stratified thin beds which suggest stratified drift. 



The clays and boulder-clays sometimes show concentric dark 

 and light-red bands cutting across the bedding-planes. These are 

 probably due to recent deposition of iron hydroxides. 



The clays and the matrix of the boulder-clays are very rich in 

 alumina. This is chiefly present as the hydrous silicate, kaolin ; 

 but alumina in an easily soluble form (an hydroxide) has been 

 found to the amount of 10'72 per cent, and 3'65 per cent, 

 respectively as the result of two analyses. This free alumina is 

 doubtless due to tropical weathering, acting on aluminous minerals 

 in the beds. 



Seeing that the earth-movements, which allowed the Mesozoic 

 granite to rise to its present position relative to the Gopeng Beds, 



