Boulder-clays, Federated Malay States. 159 



Another possible suggestion regarding these boulders is that they 

 are analogous to "core-boulders " of granite ; that they are portions 

 of beds rich in corundum and tourmaline that have resisted 

 weathering. It is known that the containing clay is sometimes 

 very rich in soluble alumina, derived, it is believed, from minute 

 pieces of tourmaline-corundum rock by the alteration of the 

 corundum, but where clearly bedded rocks are exposed, as at 

 Kacha, Redhills, and near Batu Gajah, there is, with one exception, 

 no trace of the peculiar structure of these rocks. That exception is 

 a rock found near Redhills, containing traces of Radiolaria which 

 may have been the foundation of some of the bodies in the 

 tourmaline-corundum rocks. 



It is felt now that the previously held views regarding the origin 

 of these rocks will not meet all the facts, and the objections are well 

 exemplified at Iledhills and Kacha. On the Hedhills and Pusing 

 Lama mines large boulders of tourmaline-corundum rock are found 

 in tin-bearing clay. 



At Hedhills limestone was found underneath the clay. On both 

 mines, but on higher ground, soft, weathered, bedded rocks are 

 found. On Pusing Lama a section was once uncovered, showing 

 small tin-veins in tourmalinized shales. If the clay with boulders 

 of tourmaline-corundum rock is simply the shale disorganized over 

 sinking limestone, then the shales should contain the tourmaline- 

 corundum rock too, but, as far as I am aware, they do not. Over 

 the claj^ these boulders are numerous, but over the shales they are 

 replaced by masses of ironstone formed at and near the surface 

 (Malayan "laterite"). Here, then, is what seems to be a fatal 

 objection to the clay being disorganized shale. 



At Kacha the evidence on the old mine worked formerly by 

 Towkay Ong Slew is somewhat different. On the lower part of the 

 mine there are clearly bedded and somewhat sandy rocks with 

 intrusions of aplite. Some of the hardest material has been 

 examined, and nothing was found of the structure of the tourmaline- 

 corundum rocks. On the other hand, on the high ground that has 

 been extensively worked by ground-sluicing, there are abundant 

 tourmaline-corundum boulders, some of which can be seen in situ, 

 and no bedding is to be seen now. If the bedded rocks on the lower 

 level retain their bedding, and if the rocks on the higher level were 

 once bedded, surely the conditions there are more favourable for the 

 preservation of that bedding, seeing that the strata on the top of the 

 liill are less likely to be disorganized by sinking over limestone as it 

 dissolves away than those at the base. 



Once on Pusing Lama a thin bed of clay with boulders was seen 

 under shales, and at Kacha evidence was seen of alternation of shale 

 and clay with boulders, but as these sections cannot be seen now 

 they can hardly be cited as evidence. 



Another strong objection to the theory of the clay being dis- 

 organized shale is its condition at the junction with granitic rocks. 



On the Pusing Lama mine a lode was discovered that became well 

 known. It was at the contact of a soft granitic rock and soft clay 

 with boulders of tourmaline rock and powdery tourmaline evidently 



