Western Australia. 155 



It is known that the water of hot sprinojs does contain not only COg 

 in solution but also small amounts of d'o Og. Traces of chromium 

 are contained, for instance, in the deposits of hot springs at Carlsbad.^ 

 On the other hand, there are in these fuchsite rocks small grains of 

 a black or brown colour, often surrounded by the micaceous mineral, 

 which may be chromite or picotite. At present, however, no definite 

 views as to its origin can be put forward. It must be noted that in 

 the cases previously described no tourmaline has been identified in 

 association with these rocks, so that its development may be subsequent 

 to the formation of the carbonate. 



10439. A green and white, partly siliceous, carbonate rock with 

 tourmaline, pyrite, and felspar. 



The characters presented by the rock are essentially the same as 

 those of similar rocks already described. Briefly, tiie section consists 

 of a granular mass of carbonate, quartz, sericite, and fuchsite, and 

 brown and black grains surrounded by green mica. There are small 

 aggregates of rutile needles, some in the carbonates. Apparently 

 a marginal peculiarity is a mixture of quartz, fairly fresh felspar, 

 and numerous long prisms of a tourmaline with dichroism from almost 

 colourless to brownish-green. In places the mineral is found to be 

 apparentlv enclosed both in the carbonate crvstals and in the felspar. 

 (Plate Vll, Fig. 4.) 



11028. A dark greyish-green rock with strings of pyrites, 

 veinlets of a whitish carbonate, and with a rather faint green tinge. 

 In section, besides the ordinary granular mixture, there are fragmentary 

 plates of a partially granulitized clear felspar that appears to be albite. 

 It is in places more or less sericitized. 



12257 is similar to 11028, but more heavily carbonated, and sliows 

 several veinlets of quartz with some crj'ptocrystalline areas of very 

 low birefringence. 



In 12256, which is a light-grey carbonate rock with greenish spots, 

 there are much granular carbonate, small plates of quartz, and long 

 columnar striated felspars that have been partially replaced by sericite 

 and carbonate. There are also laths of altered felspar and a large 

 number of opaque, s(|uarish, and rounded granules that appear whitish 

 or yellowish by reflected light. It was impossible to identity the 

 felspar, but the appearance of the rock is such as to suggest the 

 possibility of its having been the keratophyre. The small green 

 spots in the hand-specimen are very difficult to pick up owing to 

 their small size and the presence of sericite. It seems unlikely, 

 however, that they are inclusions. 



12317. Appears in section to be made up of quartz plates of 

 various size rendered dusty by minute fibres of sericite and small 

 bluish-green patches presumably of fuchsite. 



2. Rochs possibly of Plutonic Origin. 



11096. M.C. A weathered grey-green rock with numerous 

 grains of pyrites and occasional long thin columnar and pale greenish 

 felspars visible. 



^ Beck, The Nature of Ore-deposits, vol. ii, p. 426. 



