The cyanide process for the extraction of gold from crushed ore made possible the economic operation of non-alluvial goldfields in New Zealand, and elsewhere e.g. Australia, United States, Mexico and South Africa. The world's first field trials of the process were held at Karangahake in 1889, and the patent was acquired by the New Zealand Government in 1897. So successful was the process that the Government, through the charging of a small royalty, had recovered its initial outlay by 1905. The process involves the mixing in the tanks of the finely-ground goldbearing ore in a solution of potassium cyanide. The suspension or slime was continually agitated by compressed air. It was then trickled over a bed of coarse metallic zinc on which the dissolved gold was precipitated, to be recovered by mechanical washing. In New Zealand and Australia the tanks were known generally as B & M tanks after their developers, Brown and McMiken, but elsewhere they are commonly referred to as Pachuca tanks.
Location
List Entry Information
Overview
Detailed List Entry
Status
Listed
List Entry Status
Historic Place Category 1
Access
Private/No Public Access
List Number
135
Date Entered
2nd February 1990
Date of Effect
2nd February 1990
City/District Council
Hauraki District
Region
Waikato Region
Legal description
Pt Sec 356 Blk XVI OSD