802 GENERAL GEOLOGY OF MARULAN AND TALLONG, N.S.W., 



Analysis by W. R. Browne. 



Per cent. 



SiOa 44-82 



AI2O3 5-94 



Fe^Oa 3-17 



FeO 1 26 



MgO 1-31 



CaO 41-21 



Na^O 026 



K2O 006 



H2O + ... 0-26 



H.^0- 0-14 



CO2 — 



TiO^ 0-41 



MnO 0-13 



Total , 98-97 



N0.3 is intermediate in character between 2 and 4. 



N0.4 is a dark, very hard and heavy rock, with a somewhat 

 resinous lustre. The most conspicuous mineral is reddish-brown 

 garnet, in large masses; next in order of abundance, is bright 

 green pyroxene. Small amounts of white calcite and quartz are 

 also visible. 



Under the microscope, the rock is seen to consist essentially of 

 yellow garnet, much cracked and crowded with microscopic 

 inclusions of calcite and sericitic mica, and including small 

 amounts of other minerals. The garnet is mostly without crystal 

 form, but towards quartz and calcite it is strongly idiomorphic. 

 From other specimens obtained, it would appear that well 

 crystallised garnets, showing combinations of (110) and (122), 

 are developed on the walls of cavities; and that these cavities, 

 in some cases, have been filled in with quartz or calcite. 



Malacolite is present but not abundant, in irregular grains 

 and subidioblasts, mostl}'- about 1 mm. by Oo mm. It is colour- 

 less to slightly greenish, and shows pinacoidal cleavages in addi- 

 tion to those parallel to the prism. Some of the grains are 

 extremely ragged, and are filled with ovoid grains of garnet, 

 yielding a poikiloblastic structure. 



