Dunboyne Jasper

This site is located on private property and permission must be obtained from the landowner.

Dunboyne Jasper, Tiger Jasper, Jasper, Hokey Pokey rock or Palagonit

Whatever it is called, this interesting mineral is found only in one location covering an area of around half an hectare. The site is off the Ngpara Weston road and opposite the church, the area is locally referred to as Round Hill.

This hill was once a submerged volcano and was probably connected with the Oamaru volcanics. What is unusual with these volcanics is the presence of this yellow material interdispersed through the volcanics (basalt). It ranges in colour from yellow (like hokey pokey) to brown to dark red or a pattern of these colours.The rock has several different forms – nodular, layered, nodular on surface only to very solid (agate like) -this material was the hardness and can be polished, cut and carved.

To the east of the hill the exposed basalt when broken showed cavities that had filled with calcite – giving the ‘eye agate look’ that can be foundat the Marawhenua River.

Transactions and Proceedings of the Royal Society of New Zealand 1868-1961

Volume 19, 1886 http://rsnz.natlib.govt.nz/volume/rsnz_19/rsnz_19_00_006290.html

3. Enfield Volcano.—The railway at Enfield runs through an old volcano which extends as far as Elderslie (Section III.). It is formed principally by lava flows, which are compact and finely crystalline. Some are dark grey in colour, with small white pearly flecks, and cavities filled with limonite; these rocks weather reddish-grey. Others are darker, and without white flecks. S.G.= 2.64. I could see no olivine in any of them. Under the microscope these rocks are seen to have a microcrystalline ground-mass of felspar laths, brownish augite grains and ilmenite, more or less decomposed into leuxocene. There are no porphyritic crystals. In the absence of chemical analysis, I feel inclined to call these rocks augite andesites. At the road cutting close to the Waireka Presbyterian Church, there is a palagonite tuff composed of fragments of tachylyte and fragments of black magma-basalt with olivine. S.G.=2.35. The tachylyte is altered in places into a yellow-brown or brownish-green palagonite. I could obtain no direct evidence of the age of these rocks, and it is quite possible that the andesitic lava flows may belong to a later period than the palagonite tuffs. This is a point that requires more investigation than the time at my disposal would allow.

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