BY W. N. BENSON. 681 



excess of potash over soda was unexpected, but a duplicate 

 analysis gave almost identical figures. 



The rock passes into a serpentine like antigorite; it does not 

 appear so crystalline to the naked eye, but cleavage-surfaces 

 remain, showing a bronzy lustre [M.B., 186]. These are due to 

 the development of small schiller-plates in the amphibole- 

 cleavages. The serpentine, like antigorite, grows inwards from 

 the periphery of the grains, and forms small, dagger-like flakes 

 stabbing the residual kernels (Plate xxvi., fig. 11). 



Two curious rock-types, associated with the serpentine, may 

 be mentioned here. The chrome-bearing rock at Paling Yard, 

 east of Barraba, is quite unique as far as has been seen. It is 

 pale green in colour, crowded with spheroidal aggregates of 

 chromite about 5 mm. in diameter (or less). They may vary in 

 amount, from about 25% of the rock till, in extreme cases, they 

 are present almost to exclusion of the serpentine-matrix. These 

 spherules are made up of exceedingly minute, but perfectly 

 crystallised chromite-cubes, and sometimes contain a little anti- 

 gorite. The matrix is made up of bladed antigorite and kam- 

 mererite, the pink chrome-bearing chlorite. The latter is in 

 plates, with a low birefringence and straight extinction. Occa- 

 sionally, it shows a radial structure. The chemical composition 

 of this rock [N.T., 475] is given in Table ii., p. 705. 



The other rock-type is very different. It occurs in fragments, 

 in a water-race near the head of Oakenville Creek, Nundle; and, 

 though not found in situ, it probably forms veins in the serpen- 

 tine. The previous notice of this rock was by Mr. W. A. 

 Dixon(39), who referred to it as a kind of chlorite. He described 

 it as forming a vein in the serpentine, and stated it to be "massive 

 translucent, with a sea-green colour, waxy lustre, and unctuous 

 feel; gives a white streak and powder. In a sealed tube gives 

 off water and becomes white; before the blowpipe it is infusible, 

 but becomes opaque and reddish- white, and is not acted on by 

 hydrochloric acid. Hardness 2. Specific gravity 2-68." 



All the above statements hold for the specimens collected by 

 the writer. The physical properties are those of pseudophite. 

 Dixon's analysis (see Table ii.) does not give any recognisable 



