The goldrush to New Zealand between 1861 and 1871 involved at least 40,000 men intent on digging up gold. They came from all over Europe and the Americas, as well as Australia and China. They had come firstly to California from 1849 onwards and from there went to Australia in the 1850s. This was the first time in modern history that there was a worldwide migration of ordinary people throughout the world. And, with their arrival in New Zealand in 1861, it was the first time in the history of mankind that such a mass migration generated paper records. By them, when the goldminers started to swarm into New Zealand, the fledgling government of New Zealand was ready. There were comprehensive passenger records for the ships coming to New Zealand from the Australian goldfields in Melbourne. And then when they arrived at the New Zealand goldfields, firstly at Gabriel's Gully, then the West Coast of the South Island, and then finally, in 1867 to the Thames river in the North Island, the Gold Wardens had been appointed and they stood, pen in hand, to record the names and claims of every miner present on the goldfield, with legislation in place to enforce this great bureaucracy. In this way, the Wardens could efficiently collect the taxes and fees to run the goldfield, police it and control the swarms of unruly miners, and finally to collect the duty due on the gold exports. Most importantly, these records, at least in New Zealand, have largely survived. The equivalent mining claim records of Australia, although generated at the time, have not survived unfortunately, making the New Zealand records even more valuable.
I have devoted the last ten years to transcribing and indexing these records, which include miners from all corners of the world who converged on New Zealand 1861 - 1870. Many stayed on in New Zealand to settle, but the majority appear to have returned to their homelands with their pockets full of gold. Who were they? Was your ancestor one of them? Did your family go from poor working class in Europe to suddenly large landowners or the owners of a thriving business the next? If this transition was between the years 1861 - 1872, then you can suspect the New Zealand goldfields as being the source of sudden wealth, even if the family is unaware of this long-ago trip down under. It would definitely be worthwhile checking my online database at www.kaelewis.com where you will find the names of 60000 New Zealand goldminers.
Over the next few years, I will post more articles about the New Zealand goldrush on Steemit. 
or you can read my new book about the GOLDRUSH TO THE THAMES 1867 - 1869