BY W. N. BENSON. 683 



Many alterations have taken place. The most frequent change 

 is the passage of the felspar into saussurite, so often described 

 from other areas; but, in addition, grossularite and prehnite- 

 bearing rocks are developed, as well as other types. 



Very few fresh specimens of eucrite are obtainable The least 

 altered [N.T , 118] occurred south of Chrome Hill, Bowling Alley 

 Point. Its pyroxene (chrome-diopside) is pale green in colour, 

 almost mica-like, and is set in a matrix of clear, even-grained 

 plagioclase. The pyroxene, which is moulded on the felspar, has 

 commenced to change into tremolite, and the specific gravity of 

 the felspar (2-751 ) indicates that it is anorthite. This determina- 

 tion is confirmed by the analysis given [Table ii.]. 



The only olivine-gabbro found, occurs intruding into the ser- 

 pentine in Spring Creek, Moonbi. It is a dark grey in colour, 

 and very decomposed superficially. It consists of saussuritised 

 plagioclase, with a little prehnite forming along the cracks ; 

 diallage irregularly bounded and intergrown with the plagioclase; 

 and olivine in fairly idiomorphic grains, more or less decomposed 

 into serpentine, and bordered by a band of noticeably pleochroic 

 pink to white hypersthene, which is quite fresh. 



The pegmatitic types are best developed on Chrome Hill, 

 Bowling Alley Point. They consist of grey-brown pyroxene and 

 white felspar. Sometimes the crystals are comparatively small, 

 i.e., 3-5 mm., in diameter, but usually they are much larger; 

 diallage-plates more than 5 cm., in length, have been collected. 

 These rocks frequently show ophitic structure very well developed 

 in hand-specimens. A little magnetite may also be visible. 

 Under the microscope, the diallage of most coarse-grained speci- 

 mens was found to be more or less akered to tremolite, lying 

 parallel to the vertical axis, or occasionally in a small knot of 

 fibres. Dotted about the plate, and occurring especially around 

 the periphery, are small, brown flakes and bands of hsematiteC?). 

 The felspar is completely saussuritised, and there are a few 

 irregular veins of prehnite. The smaller-grained examples [N.T., 

 7] are more interesting. The felspar is less altered. The diallage 

 shows some peculiar intergrowths of several individuals of pyrox- 

 ene. Along lines of cleavage, fracture, or other plane of weak- 



