Welcome to the forum steddy, although i am not from new zealand i enjoy reading and trying to learn about the gold mining and where it is located on the coromandel,
a few years back i bought a book called coromandel gold,and its a guide to most of the gold fields and mines on the coromandel,it also gives you tips where you might get lucky its pretty comprehensive, bought it at one of the big book stores in auckland, i am going to post a picture of the book cover hope it comes out ok i just took it with my phone.
Good luck .
Mem.