26 T. S. Hart : Tlie M Ineralog leal Characters 



similar conditions. It may also happen that what appears to be 

 one reef may consist of parts of quite different mineralogical 

 types. 



The following mineral associations may be recognized, being 

 cliaracterized by the presence or prominence of the minerals 

 mentioned in each case. 



1. The ordinary type. — Pyrite or arsenopyrite or both, 

 prominent among the metallic compounds; with sphalerite 

 and galena commonly present in small quantities. 



2. Galena and sphalerite prominent with pyrite. 



3. Stibnite. 



4. Chalcopyrite. 



5. Siderite and chalcopyrite. 



6. Pyrrhotite and chalcopyrite. 



7. Molybdenite usually with pyrite. 



8. Bismuth minerals. 



9. Wolfram. 



10. Cinnabar and mercury. 



1. The association of minerals in this type, as ordinarily 

 occurring, may be more fully stated as quartz, albite, dolomite, 

 pyrite, arsenopyrite, galena, gold. Carbonaceous matter is also 

 frequently present, sometimes as graphite. 



The albite and dolomite are quite subordinate to the quartz in 

 quantity. The sphalerite and galena, though in much less 

 quantity than the iron rainerials, and less generally distributed 

 in the reef, are often persistently present in the richer portions. 

 Of tiie two iron compounds one or other may be more prominent, 

 or both equally so. The proportion of the metallic minei'als in 

 the reef varies greatly. There are of course many reefs of this 

 type from which a part only of the series is recorded. 



Dolomite and albite often escape notice in the bad light in the 

 mine, but are easily recognised in most cases by their cleavages. 

 Albite is often altered to kaolin to a considerable depth from the 

 surface, and pholerite also occurs in the cavities of the quartz. 

 Dolomite is often evident on the old material on the mullock 

 heaps, as it contains a little iron carbonate which causes it to- 

 turn brovvn on exposure. In the Ballarat mines it occurs in four 

 forms, impure grey dolomite in the country rock agreeing with 



