THAMES GOLDFIELD.

Thames Star, Volume XI, Issue 3516, 2 April 1880, Page 2

THAMES GOLDFIELD.

The following is Dr Hector's report upon the goldfieM, the result of his Visit t» the Thames.

This gold-mining district was visited in February last, andj owing to the great amount of work which had been done since my prerious risit, I was able to obtain satisfactory confirmation, of the views which I had previously expressed as to the mode in which the auriferous reefs occur, and which may be summarised as follows:— The rock in which the quarts reefs are found is a massive formation of igneous tufa, passing on the one hand into .a compact greenstone trachyte, and on the other into a coarse breccia rock, 'consisting of angular fragments imbeded in a tufaceous cement. The age of this formation is still uncertain; but at Tapu Creek it rests upon the slate rock, and tt Ooromandel it is overlaid [by the brown

coal, which again is overlaid unconformably by a younger rolcanie formation, which is referred to the Eocene period. The tufas in which the auriferous reefs are found should therefore, in all probability, be referred to some part of the Cretaceous period.. From some reason not yet ascertained, this formation of tufa has been decomposed to a great depth, and in a very irregular manner, the undecomposed rock "forming hard ridges thas reach .the surface, separated by belts of soft ground extending to many hundred feet below sea-level; and in these latter productive quartz veins have alone betn found, and, so far as is at present known, they are pinched cut, or become unremunerative, on entering the hard andecomposed rock. • . _• „ Much capital has been expended 1 in an unproductive manner in driving'through these hard ridges, without any idea of their size or form. The future develop, ment of the field appears to depend upon the accurate definition of the extent of area and the depth of the decomposed rock; and the exploration necessary to accomplish this could, in my opinion, be better effected by the use of the diamonddrill than by the present expensive system of shafts and tunnels. The proposal to explore the auriferous belt by a tunnel two miles in length, between the Tararu and Karaka creeksrespecting which my opinion was specially sought—doesnotthereforeseem tome to be the most satisfactory method of prospec**** ing the country, as an examination of the ■ ground shows that at least for flve-sixthi of the distance the tunnel would be earned through hard undecomposed rack, in which. from experience productive reefs could hardly be expected to occur.