Waihola Chert

This site is on private property (lifestyle blocks) Permission required.

Having explored much of the Lake Waihola (once a shallow, tidal, Waihola / Waipori lake complex is the remnant of the former marine inlet – based on Quaternary (2-3mya) sediments while the hills are generally made up of Cretaceous Henley Breccia) area. In my early years I came across rock piles of this material but took no notice of it. It was stacked up in small piles at the southern end of the lake by the big blue gums. In those days of the early 70’s I was more interested in the apple trees and one lonely solitary pear tree – great for eating after an early mornings fishing or rabbit hunting.

These rocks made their appearenace when the paddocks were ploughed. (I have never seen this chert along the lake edges).

This material is extremely hard and chert rocks have a rough texture – they are not water worn. When broken the edges are sharp and in the old fracture joints are minute quartz crystals. Apparently this CHERT is associated with limestone in the area but how they come to be in the paddocks far from limestone atop old Quaternary/fluvial sediments is a puzzle.

From - Transactions and Proceedings of the Royal Society of New Zealand 1868-1961 Volume 10, 1877 pg 495

Of the colour of yellow-ochre; cavities lined with bluish-coloured quartz and chalcedony? The translucent grey portions, when heated in a closed tube, decrepitate somewhat, give off water, a slight white sublimate and fumes of sulphurous acid; does not blacken; the ochre-coloured portions give off water, a slight sublimate similar to the last is formed, and an empyreumatic odour is evolved; the residue blackens (but finally burns to a reddish-brown, due to the presence of iron oxide), and the condensed water has a strongly alkaline reaction, all of which tend to indicate that organic matter is present. The hardness of the ochre-coloured part is greater than that of the grey portion, the former being about 6.5, and the latter not more than about 5.5.

The blue-grey portion appears to be a film of chalcedony (or hyalite) coating small and imperfect quartz crystals.