388 MK. J. B. SCKIVENOR OH" THE [Aug. I9°9> 



The question whether the Lahat pipe is a ' lode ' or a detrital 

 deposit has interested many people in this country ; but, until lately, 

 I have been unable to obtain satisfactory evidence to lead me to a 

 definite conclusion on either side. The manner in which prisms 

 of cassiterite and fragments of acicular growths of the same mineral 

 were mixed up in the matrix pointed to its being a detrital deposit ; 

 but a specimen presented by the Societe des Etains de Kinta to 

 the British Museum (Natural History) in October 1905 showed that 

 this could hardly be held to apply to the whole deposit. Pig. 3 

 (p. 386) is a reproduction of a photograph of this specimen. It 

 shows distinct thin veins with included fragments of limestone, and 

 it also exhibits a ' caunter vein '. But a microscopic examination 

 of small fragments of the ore, which is of about the same colour 

 as the typical pipe-ore, showed quartz-grains that might be water- 

 worn, one or two round grains of zircon, one round grain of rutile, 

 a quartz-grain with rutile hairs, a trace of biotite, and some 

 yellowish-brown tourmaline. 



But since I gave, in the publication referred to above, the 

 arguments for and against a ' lode ' or a cemented detrital deposit, 

 further evidence has come to light, which leads to a very interesting 

 conclusion. I have already recorded the occurrence of a cave at 

 80 feet, having its floor partly coated with ore. 1 At greater depths 

 other caves have been found, most of which contained a thick 

 layer of stratified iron-ochre with cassiterite and nodules of sili- 

 ceous rock resembling the silicified limestone from the wall of the 

 pipe. One cave, coated top and bottom with beautiful calcite- 

 crystals, contained no ore or iron-ochre, but water only. 



Additional specimens were obtained, too, at a greater depth of 

 small veins in limestone like that figured ; but the most illuminating 

 specimen found was one of which a diagrammatic sketch is given 

 in fig. 4 (p. 387). But for the fact that the arsenopyrite is partly 

 oxidized, this could not be distinguished from specimens of ore 

 from the Ayer-Dangsang pipe ; and the evidence of this specimen 

 and of the caves with their ore-deposits leads me to conclude that 

 originally the Lahat ' pipe ' was a deposit like the Ayer Dangsang 

 ' pipe ' and others, and that the deposit offered a convenient course 

 for surface-waters which dissolved away the calcite- matrix and 

 allowed the sulphides to become oxidized by the oxygen in the air 

 accompanying the water. Caves were formed, into some of which 

 a mass of iron-ochre and cassiterite was washed, together with 

 nodules of silicified limestone dissolved out of the wall of the 

 pipe. Later the flow of water ceased, and the disorganized mass of 

 cassiterite and iron-oxides was recemented by calcite from the 

 walls of the pipe, which still retained the same form as that which 

 it originally possessed. 



i ' Report of Progress' 1903-1907. 



