Notes of Books and Papers. 148 
of some altered basic rock, with no prevailing direction, that are 
found more frequently in the sedimentary strata than in 
the granite, sometimes as intrusive sheets along the bedding 
planes, elsewhere following joint planes, even at times penetrating 
quartz veins. These dykes are the source of the tin, which is 
found only as the binoxide, cassiterite, or “tin-stone,” running 
irregularly through the gangue in fine “stringers” or “ leaders,” 
that often swell out into large bunches, or else the ore is finely dis- 
seminated throughout the whole mass. As would be expected, 
more or less “stream tin,” from the disintegration of the dykes, 
has been obtained by washing the alluvial bottoms of the gullies. 
In mining, some of the claims have done considerable explora- 
tion work, and the ore has generally been found associated 
with galena, iron pyrites and more or less arsenical pyrites. 
The ore is concentrated to a form of rich matte, or “ black 
tin,” preparatory to shipment to the smelters, by roasting 
it in large calciners, and from 1884 to 1888, from 4,851.5 tons of ore 
crushed, the yield of black tin was 352.6 tons. ° 
This Coolgarra tin deposit is interesting and peculiar from the 
fact that the mineral is found in these dykes of basic rock, while 
in other parts of the world tin is found for the most part in granite, 
in “stockworks,’ or masses traversed by many minute veins 
which necessitate the working of the whole mass to gain the 
ore. In Saxony large areas of porphyry have been mined 
for tin, but we can find no record of tin being found under such 
conditions as those described above. 
It is strange that as yet throughout the world the areas in which 
tin is found are so few and limited in size, and that on this conti- 
nent, which has been so prodigal in its production of all other metals, 
tin in sufficient quantities to be mined profitably’ is almost 
unknown. It holds such a strong place in commerce, where it is 
of such great economic use in tinning iron plates, and for the 
manufacture of bronze, bell metal, pewter, Britannia metal, etc., 
that there is a firm and growing demand for it, and any new area 
reported as productive of this metal immediately receives great 
attention, though many false alarms have resulted from men mis- 
taking zinc blende, or “ Black Jack,” for tin stone, or by men manu- 
facturing alluvial tin deposits, or placers, by importing several 
barrels of ore from Cornwall, and sagaciously scattering it about at 
some suitable spot, deluding some unsuspecting speculators into 
buying what they thought was better than a gold mine. 
W. A. Cartyiy, M.E. 
