723 
No. 29. Neab Bathtjbst (New South Wales). 
The late Mr. C. S. ATilkinson’s Collection. Sp. 6r. 2'993. 
A black, fine-grained, compact rock, the faces of some of the constituents 
glistening ; weathering yellowish-grey, and spotted ; rarely with zeolites. 
Section . — The ground-mass contains fine lath-like felspars, a little glass, por- 
phyritic augite, and olivine with plentiful black grains of magnetite or titaniferous iron. 
The felspars show fluxion-structure, arranging themselves in little streams dividing 
before, and closing up after meeting an obstructing porjfliyritic crystal in the flow. The 
felspars are about ‘01 inch in length. A greenish secondary mineral matter is often 
secreted along the augite cracks. Magnetite frequent, enclosed in the augites. 
No. 30. Bathurst (New South Wales). 
The late Mr. C. S. AVilkinson’s Collection. Sp. Gr. 2'951. 
Black, compact, with occasional spots of zeolites. Weathering to a yellow 
ochreous colour. 
Section . — The ground-mass contains fine lath-like felspars, with very minute grains 
polarizing in high colours, probably augite, and very little glass. The porphyritic augites 
are as a rule fresh, though in some ca.se.-i the secretion of greenish matter is to be observed 
along the very irregular cracks. Some water-clear plagioclase felspar.s occur with a very 
wide angle of extinction between broad and handsome lamollis, polarizing in a low colour. 
The highest angle of extinction observed w-as (13° 30', and the lowest 32°. The fluxion- 
structure is even more prettily marked than in No. 29. One of the augites shows 
distinctly cross cleavages (which, however, are not very regular) parallel to the face 
00 P. Another augite shows twinning in an interesting manner, there being three lines 
along the suture, as in the section of the Gympie augite illustrated on Plate 65, Pig. 2. 
The whole section swarms with magnetite. 
No. 31. Mount Sassafras (New South APales). Intruding through the Hawkesbury 
Formation. 
The late Mr. C. S. AVilkinson’s Collection. Sp. Gr. 2'816. 
Greyish-black. Crystals quite visible owing to reflection. No zeolitie matter. 
Section . — The ground-mass has very little glass, and is much charged with 
a dirty brownish-green opaque matter. Magnetite and plagioclase felspar.s. On the 
margin of one of the olivines is a stellate group of secondary secretions, which polarize 
in the aggregate, one portion certainly spherulitic. Augite and olivine occur por- 
phyritically, the latter a pinkish-brown, and dark, polarizing in high colours, and much 
pierced and riddled by the felspars. Crossing the junctions are fine needles, probably of 
apatite. The latter also abounds throughout the ground-mass. Magnetite is plentiful, 
as is probably also titanic iron. 
A rather large augite crystal is traversed by cracks, along which there are 
secondary deposits. Their pleochroism is exceedingly remarkable, in some eases sky 
blue, yellow, and green, very distinct. The periphery of this large crystal is marked by 
a dark-brown zone, and extending radially into the contiguous ground-mass is a fine, 
delicate, semi-translucent, aggregately-polarizing fringe. Arranged in the same way 
under the ^-inch objective, this fringe is seen to be composed of fine microliths, clear, 
and rather short, very much crowded together, ow'ing to which there is no extinction in 
any azimuth. The augite is rich in gaseous pores. 
