85 



:notes on a fossil wood from cox's bight. 



By W. a. McLeod, B.A., B.Sc. 



There being, so far as I can ascertain, no description or 

 notes in the Papers and Proceedings of the Royal Society of 

 Tasmania on replacement fossils of Tvood by iron pvrites, it 

 seems to me not out of place to record some observations on 

 an interesting specimen of this nature from the locality of 

 Cox's Bight, and kindly placed at my disposal by Mr. Alex. 

 Morton. 



This specimen was discovered in the tin deposits at Cox's 

 Bight. 



In appearance it is rather deceptive, and at first sight its 

 upper half seems like graphite, being of a dull greyish-black 

 colour. The streak also would be apt to deceive, being some- 

 what like that of graphite. The extension of the upper half 

 is smooth, showing a slight longitudinal graining, whilst on 

 the ends traces of the original fibres of the wood mav be 

 seen. The upper half is united to the lower in a very 

 distinct manner, just as if the two pieces had been cemented 

 together. The lower and larger half is of ;tn entirelv different 

 nature in certain respects to the upper. Its surface, though 

 in a certain degree rounded, is rough., and has the appearance 

 of a fragment of a holocrystalline rock of medium texture 

 which has been subjected to friction in the bed of a river. 

 Embedded in it can be seen b}- the naked eye small grains of 

 quartz of a subangular and rounded nature. On fracture the 

 two halves exhibit striking differences. In the upper half it 

 may, perhaps, be best described as like that of a piece of charcoal 

 wood, and being at right angles to the grain of the specimen, 

 though of a slightly rough and uneven character, and the fresh 

 face is of a metallic-grey colour. The lower half, on the other 

 hand, presents a coarse hackly fracture like that of cast iron, 

 and shows small embedded grains of quartz of a subangular 

 nature. The colour of the fresh face is like that of the upper 

 half, being a metallic-grey. 



The total length of the specimen is about three inches, the 

 width about three-quarters of an inch, the depth about one 

 inch, the lower portion being larger than the uppjer. 



The hardness of the upper half was rather difficult to 

 obtain ; the outer surface can be pared away with a knife 

 like a piece of graphite, on account of the finely-divided state 

 of the iron pyrites, but on fracture both the upper and lower 

 portions have a hardness approximating that of iron pvrites 

 (6 to 6-5) 



The specific gravity of the upper portion when taken by 

 weighing in air and in water is low, being 3-5 instead of 4*5, 



