134 ORIGIN AND MODE OF OCCURRENCE OF GOLD-BEARING VEINS. 



rocks, of which syenite is the most prevalent. A sandstone, 

 known as " Daintree's Desert Sandstone," at one time doubtless 

 overspread the country, but has been almost entirely denuded, 

 and only now remains, capping the higher ranges in the district 

 where it forms steep escarpments of horizontally bedded rock. 



In places narrow belts of highly altered slates and sandstones 

 occur, which have been caught up in folds of the syenite, and are 

 the last remnants of the sedimentary paheozoic rocks of the 

 locality. They have been greatly altered, some of them being 

 converted into quartzite, are highly charged with iron pyrites, and 

 are intersected by numerous feldspathic dykes. One of these belts 

 may be traced in a north easterly direction from a point 

 immediately south of Mount Morgan, and is closely bounded to 

 the south, east, and west by the syenite. In this belt a wide 

 lode formation occurs, striking 1ST. 30° E. (which is approximately 

 the strike of the belt of rock enclosing it), and having all the 

 appearance of a large dyke. It underlays to the east at an 

 angle of 10° to 15° from the vertical, and has a banded structure 

 parallel to its strike and underlay. 



In Mount Morgan itself this lode consists in the higher levels 

 of alternate bands of ironstone (limonite) and honeycombed or 

 porous quartz (with much foreign matter), these bands having the 

 same strike and underlay as the lode, and most probably changing 

 in the lower levels into a dense quartz or numerous veins of 

 quartz, through which a large quantity of iron pyrites is 

 disseminated as minute crystals ; veins wholly of iron pyrites 

 may also exist below, that have decomposed on the surface in 

 limonite iron ore. The entire width of these layers of ironstone 

 and quartz with intervening bands of altered rock at Mt. 

 Morgan is about 1500 feet, but those that constitute the main 

 lode that is being worked comprise about two or three hundred 

 feet in width. It appears that the narrow belt of altered strata 

 in this place must have been fractured and opened into immense 

 fissures or a number of parallel fissures which have been filled in 

 with lode matter and probably afterwards undergone re-opening 

 from time to time, and a re-filling with or re-depositing of the 

 quartz and other minerals constituting the lode. Feldspathic dykes 

 which have decomposed to kaolin are also found traversing the 

 lode and parallel to the bands of ore in it. 



The honeycomb quartz is doubtless the result of the 

 decomposition of the pyrites, the resulting limonite having been 

 dissolved out and probably redeposited with other matter in open 

 fissures to form parts of the bands of ironstone described above. 

 Every stage of the change can be illustrated by specimens from 

 the mine, the quartz charged with minute crystals of pyrites 

 giving place to a quartz in which crystals of pyrites yet exist, but 



