“...Rangiatea Station is a privately owned foothills farm in the general Mt Somers area of Mid Canterbury.
No collecting is allowed on the property these days but several years ago it was possible to dig there on a fee basis. The agates being dug were called "magpie agates" initially and they were deposited in ancient river banks or  shorelines that are no longer near our present coastline.
The clays and muds encasing the agates have been responsible for their deep staining, particularly into  the softer layers of the water level banding where it has left unusual contrasts between them. An interesting effect can be gained by cutting these agates parallel to the onyx banding and still be left with what appears to be a wall banded agate.
Many of these agates show evidence of a very tortured journey to where they now lie and we do not know for sure their original birthplace. The predominant colors are browns, yellows, brickish reds, pinks and blacks. There are also some very beautiful egg shell patterns that resemble morrisonite jasper characteristics.
In the Hinds River Gorge which also runs through Rangiatea, there are other nicely colored agates to be found , including the greens rather similar to Gawler Downs...”

pers. report of Malcolm Luxton, Canterbury