Pounamu, Greenstone and New Zealand Jade are all names for the highly valuable and precious stone used by the Maori people of New Zealand for making adornments, tools and weapons. Pounmau being the tradition Maori term, Greenstone being the more commonly used term, and New Zealand Jade being the gemological term.
Pounamu is found only in the South Island. Because of this, the island was originally named Te Wāhi Pounamu (the place of pounamu), but over time this name changed to Te Wai Pounamu (the greenstone waters).
The main deposits used by Māori are in the districts around the Taramakau and Arahura rivers in Westland, coastal south Westland and the Lake Wakatipu area in Otago. In addition, there is a significant field of bowenite in Milford Sound (Piopiotahi).
Geologists have determined that nephrite and bowenite formed deep in the earth, probably at depths in excess of 10 kilometres. Hot fluids caused a chemical reaction in zones where volcanic and sedimentary rocks were in contact, which produced narrow deposits of pounamu. High-quality pounamu is usually surrounded by altered material classed as serpentine.
As the mountains of the South Island were formed over the last two million years, the narrow bands containing pounamu were lifted up to the earth’s surface. The action of rivers and glaciers released the stone from its host rock into screes, river gravel and glacial deposits. Pounamu continues to be carried into rivers and down to the sea by erosion. In the more accessible areas, any exposed pounamu has been quickly collected.