The Monowai Mine was an epithermal gold and silver mine operated from 1891 to 1915 producing 1,240 kg of bullion.
It 1983 there was an application to reopen the mine, which was opposed by local groups (including the Coromadel Watchdog and Thames Coast Protection Society). In 1991 the area was protected under schedule 4 of the Crown Minerals Act 1991 which protected (amongst other areas) "All Crown owned land held under the Conservation Act 1987 or any enactment set out in Schedule 1 of that Act on the Coromandel Peninsula that lies north and north-west of State Highway 25A (Kopu-Hikuai road) and the road from Hikuai to Pauanui Beach known as the Hikuai Settlement Road". The debate was reopened in 1997, and is still going on today.
The cache is at the Monowai Battery. Stamper batteries crushed quartz into powder and numerous were set up in the Coromandel ranges. They were highly inefficient (only 45% of the gold and barely any silver was recovered), and were replaced by a process in which cyanide was added to crushed quartz ore. Gold and silver were dissolved in cyanide, allowing more of these metals to be recovered (about 90% of gold and 50% of silver). They were extracted from the cyanide solution using another chemical process, and the resulting concoction then flushed down the Waiomu River, an act so egregious that a Mr RR Trotter sued the Monowai Gold Mine Limited for 50 pounds over it in 1899.
The cache is in the battery area, safe for kids, with the track right to it.