&7 



EXPLAXATIOy OF PLATE. 



Fig. 1. Vesicular melaphyre from Silver Queen Mine, Zeehan. x 75. 

 Crossed nicols. The large vesicle to the right is filled with a crystalline 

 calcite aggregate, showing twin lamellae. Near the bottom of the vesicle, 

 and included in it, is an amygdule of delessite. The vesicle to the left is 

 also occupied by twinned calcite, and contains a subordinate cavity filled 

 with calcite and fringed, like the main vesicle, with delessite. The latter 

 mineral is represented in the figure by a white border. The black grains 

 in the field are the iron ores. The white patch at the top of the field is 

 part of a resetted delessite amygdule. 



Fig. 2. Same as No. 1. x 75. Crossed nicols. The centre of the field 

 is occupied by a large cavity filled with calcite and Eringed with feebly re- 

 fracting delessite (white in the figure). The twinning lines of the calcite 

 are intersected diagonally by the cleavage planes. The half dozen white 

 apots in the calcite represent delessite amygdules in the interior. 



Fig. 3. Same as Xos. 1 and 2. x 75. Crossed nicols. The cavity to 

 the left, with its delessite border, contains twinned calcite, and in the 

 centre of the latter is a small delessite amygdule. The orientation of the 

 calcite is not disturbed by the small amjgdule. This shows that the 

 crystallisation of the calcite and delessite was synchronous. The white 

 amygdule to the right is a delessite rosette, containing some carbonate of 

 iron. 



Fig. 4. Melaphyre from Silver Queen Mine, Zeehan, 120ft. lerel. x 100. 

 Ordinary transmitted light. This shows the felspar laths with iron ore 

 pseudomorphs as black strings and microliths. 



Fig. 5. Dolerite from Cataract Quarry, Launceston. x 75. Crossed 

 nicols. Half of the figure is occupied by a large compound plate of augite 

 with a border of magnetite grains. The rest of the field shows crystals of 

 triclinic felspar. 



Fig. 6. Dolerite from same locality, x 75. Crossed nicols. Augite 

 crystal lying tranavertely in centre of figure ; felspara occupying re- 

 mainder of field. 



