48 ON SOME NEW SOUTH WALES MINERALS. 
5. The fissures in the pyrites nodules were next filled in, in 
some cases with pyrites in others with quartz ; it may 
have been that the latter were also filled in first with 
pyrites which was afterwards dissolved out and replaced 
y quartz. 
6. Finally the marcassite has been removed and the silicious 
septa set free (fig. 3). 
The pyrites of the nodules oxidizes with great rapidity : speci- 
mens kept for only a few months rapidly fall to powder, and 
ome incrusted with crystals of iron sulphate. 
[Two photo-lithographs.] 
