Based on Rock glazes of NZ
Sample 15: Pink Granite
A light colour rock made up of relatively large (up to 1/2") crystals, pink feldspar quartz and mica are all visible in the specimen. Common in parts of Nelson and Westland e.g., Buller Gorge, various parts of Fiordland and Stewart Island. (Granite has a similar chemical composition to rhyolite and obsidian.)
This has been my favourite sample so far and I'm surprised how easy and abundant these samples are to gather. When searching online for locations of pink granite the Buller Gorge Swingbridge Adventure and Heritage Park showed in the results. They were more than happy for me to gather a couple of rocks from the river bed. The river was raging after a night of heavy rain, after crossing the swing bridge and heading down to the jet boat jetty there were many loose rocks scattered about. I would advise though that further down the gorge at the game fishing spots there are many other more accessible rocks.