Bulletin of the Geological Society of Malaysia, Volume 8, Dec, 1977, pp. 131 – 136
Jabatan Geologi, Universiti Malaya, Kuala Lumpur
The Bylco Azira mine is a deep opencast one, approaching 100 ft. in depth from which cassiterite is being recovered from those portions of the placers that largely occur between the pinnacles of the marble bedrock, and so were inaccessible to the dredges which had previously operated there. The mineral is also recovered from certain lodes and veins in the mine.
On the floor of the mine two major lodes are exposed that pinch and swell and vary in thickness from c. 1 to c. 4 ft. Associated with these is a swarm of veins with a markedly different strike from that of the former, but the age relationship between the lodes and veins is still in doubt.
The veins are characterised by the presence of cassiterite and pyrite, whilst the lodes contain, in addition to cassiterite and quartz, an impressive suite of sulphides that probably includes stannite. In any event, a stannite-rich block was found near one of them and peripheral material from this, when examined in polished section, provided the data for this note.
The polished sections from the block consist of cassiterite and quartz associated with early pyrite and arsenopyrite, and somewhat later sphalerite, stannite, (tetrahedrite?) and chalcopyrite. In particular, the earlier sulphides are markedly veined and replaced by the later ones. The paragenesis and texture of this ore will be treated in detail in a later note. In this note the writers will confine themselves to the nature and genesis of a most interesting sulphide rim as revealed in the polished sections.