SOO GKNKRAL GKOLOGV OF MARl'LAN AND lALLONG, X.S.W., 



what siliceous. Taking this specimeu as the origin for distances, 

 the other specimens were situated as follows : — 



Xo.2 5 feet 



Xo.3 9 feet 



No. 4.... 15 feet 



No.5 IS feet 



No.6 22 feet 



No. 1. Coarse granular marble, composed almost entiiely of 

 calcite with a little light yellow garnet, and a few tlakes of 

 phlogopite. 



Xo.2. Coarsely granular rock of very striking appearance. 

 Macroscopicall)- it has an apparent grain -size of about 3 mm. It 

 is composed chiefly of a pearly-white prismatic mineral with 

 perfect cleavage (wollastonite). and a dark reddish mineral 

 without cleavage, which, in tlie field, was taken for garnet, but 

 which is really vesuvianite. (Plate Ixix., fig.-. l 



Under the microscope, the most abundant mineral is vesu- 

 vianite, in large poikiloblastic grains up to 1*2 mm. by 10 mm. 

 These are optically continuous throughout, though very ragged 

 in form. Some are so crowded by large grains of garnet and 

 opacite as to approach sieve-structure. In thin sections the 

 colour and pleochroism, though noticeable, are not very intense; 

 in a section 075 mm. thick, the pleochroism is very strong, O 

 faint yellow, E bright rose-red. Double refraction is extremely 

 weak, and even thick sections give only a peculiar azuie tint 

 between crossed nicols, and scarcely alter the interference-colour 

 of a gypsum-plate, giving red of the first order. The optical 

 sign is positive throughout, and therefore abnormal. 



Next in order of abundance is a colourless pyroxene mineral, 

 probably wollastonite. Most of the characteristics agree per- 

 fectlv well with those of that mineral; colour, cleavage, refrac- 

 tive index, double refraction, axial angle, optical sign, and dis- 

 persion are quite normal. A point of interest is, that cleavage- 

 chips show quite a constant small departure from straight extinc- 

 tion ; they all extinguish at an angle of 3"^ from their length. A con- 



