6 
metamorphosed — -form the chief matrix of the tin ore in the porphyry country. The 
ore (binoxide of tin) occurs in floors, veins, or pipes, among the joint-planes of the 
dykes. It is rarely crystalline; but occurs either in amorphous masses, almost 
chemically pure, or intermixed with the dyke rock. Sometimes, as in the Bradlaugh 
Mine, the ore is so finely disseminated through the dark chlorite matrix as not to be 
distinguishable by the naked eye. These “ chlorite ores ” generally weather of the 
colour characteristic of iron peroxide, and in such cases the tin ore is rather more 
obvious. Fluorspar and wolfram are associated with the ore, but tourmaline is of rather 
rare occurrence. 
It seems most jirobable that the tin first came up in solution after the consolida- 
tion of the dykes and has been deposited along their walls and among the fissures and 
joint-planes which traversed them. A re-solution of the tin ore probably took place 
simultaneously with the metamorphism of the dykes ; and as the metamorphosed dykes 
had probably a new joint system developed in them, a further concentration of the ore 
may have taken place. 
Considerable difficulties were at first experienced in following down the apparently 
ca])ricious ore deposits, and the miners were haunted by doubts as to their continuance 
at greater depths. It has always seemed to me that their intimate connection with 
dykes was a sufficient guarantee of their great vertical range. The Grreat Northern, 
which has maintained from the beginning its position as the leading mine in the porphyry 
country, is now turning out ore from the 400-feet level. 
In the sedimentary country-rock the group of mines now united in the North 
Australian Lease, near Watsonville, was the first to attract attention. In these mines, 
especially in the North Australian and Ironclad, the lodes, although themselves some- 
times poor for a distance, sent off huge “ carbouas ” of tin and copper ore along the 
bedding-planes of the shales and groywackes. In 1883-6, this group of mines yielded 
1,287 j tons of dressed tin ore, valued at £64,382. Important discoveries of silver and 
copper ores in this country have recently been reported. 
More recently very important lodes of tin ore have boon opened up in the 
sedimentary rocks at Irviuobank (Great Southern, &c.), in Glen Linedale, and at 
Denny and DogherLy’s Camp. In the Irviuobank lodes the ore is generally of the 
“ chlorite ” type, and in the Great Southern Mine it is associated with arsenical pyrites, 
bismuth, stihnite, &c. In the Gordon, in Glen Linedale, the ore impregnates a country- 
rock of hard, fine-grained, siliceous, and talcose sandstone. At Denny and Dogherty’s 
Camp very fine crystals of tin ore are disseminated through a chloritic matrix in lodes 
which coincide with the bedding of the country-rock (pebbly grits). 
There is little doubt that the stanniferous sedimentary rocks of this district are 
part of the same mineralised belt wdiich has produced the lead and silver ores of Mount 
Albion and the Dry Liver. 
Considering the amount of lode tin obtained in the district, the yield of stream 
tin has been insignificant. A. considerable quantity, however, has been taken from a 
deep lead covered by basalt in the valleys of Nigger Creek and the Wild River. 
For detailed information regarding the lodes the reader may be referred to — 
(1) Report (R.L.J.) on the Wild River Tin Mines, 27th October, 1880, in 
Further Reports on the Progress of the Gold Prospecting Expedition in 
Capo York Peninsula, 1881. 
(2) Report (R.L.J.) on the Tin Mines of Herberton, &c., 1883. 
(3) Report (R.L.J.) on Mineral Lease 276 (North Australian), Watsonville, 
1887. 
(4) Report (R.L.J.) on the Chillagoe and Koorboora Mining Districts, 1891. 
