Since the northern motorway was completed in the 1971, countless numbers of New Zealanders have driven blithely by a cluster of huge round boulders in a farm field beside the Whangaparoa turnoff, unaware of the significance of what they're getting a fleeting glimpse of (sound familiar?).

One of the cluster of huge spherical boulders that was lying very close to the surface on the slopes of the highest hillock just north of Silverdale on the approach to Orewa. The roading crew were obliged to move these massive stones to the edge of the new highway. Yet more of these spherical boulders were found when the highway was widened a few years later.

An archival photo from 1971, showing the first of the huge boulders unearthed between Silverdale and Orewa on the side of a hillock at the highest point of the new highway. In latter years it was necessary to widen the highway yet again at the same point of the road and encroach yet further into the farm of Croix and Alex Grut, at which time more and larger spherical boulders were found. Photo supplied courtesy of the Wainui Historical Society, Silverdale.

I was recently reminded about these anomalous boulders by a friend, Graham Cunliffe. Graham, a former Orewa lad and avid motorcyclist, used to "hoon" past these amazing boulders daily on his way to work in the city. They had made an indelible impression on him and always seemed strangely out of place and mysterious. Why were they there in such a large, concentrated grouping? It almost seemed like they were hauled in from somewhere else and placed there for some reason. If Graham hadn't of reminded me about the huge round boulders at the extreme northern edge of the Auckland Isthmus, it might have been a very long time before I remembered to "go and check them out".

According to the memories of some long-term residents of Silverdale, the find of these many boulders, all at the same high spot, raised a number of intriguing questions regarding how they got there. There was considerable, initial interest shown, spurned on by commentary on talk-back radio, that raged for days. It was very mystifying as to how a cluster of huge round boulders were all found atop the highest hill in the Silverdale-Orewa region. They obviously came from the Wade River Estuary or in the tidal stream near the Orewa bridge, where they occur naturally and can still be found. At the "Pioneer Village" at Silverdale a caption beside a photograph of some of the boulders found on the nearby hill states:

These are concretions, formed much as a pearl forms in an oyster. Lime dissolved in ground water has at some distant time in the past collected, possibly around a pebble or shell, and cemented sand grains in a slowly growing sphere. The famous boulders at Moeraki in the South Island were formed in the same way.

Private trucking contractor, Noel Shaw, under contract to the Ministry Of Works, remembers well the circumstances in which the boulders were found. Noel recounts how the old road north out of Silverdale wound up and around a long steep hill, starting at the northern edge of Silverdale township. It was decided to do a deep and long cutting to the western side of the existing road and flatten out the hill to form a motorway. The boulders were encountered by the motorscraper on about the first cutting of the surface at the crown of the hill. Thereafter, bulldozer driver, Jim Woolly and the digger driver had to dig round them to expose them for removal. The surrounding terrain was made up of yellow clay, but the boulders were limestone & sand concretions, that only form in seabed or other watery sediments. There was nothing in the surrounding terrain that could provide either the environment or materials to form the boulders.

Site forman, Clarie Neville, was interviewed by newspaper reporters and asked about the boulder find. Mr. Neville stated that he was mystified as to how these boulders got to the top of the hill. Geologists, were going to investigate the matter and write up a report, but the idea died a natural death and no satisfactory explanation for the presence of the boulders at that high inland location was ever forthcoming.

Noel Shaw remembers driving his dump truck to the job in the semi-darkness one morning, only to see a low-loader truck, transporting some of the huge boulders, pass him driving south. Apparently a highly placed Auckland City Council official had organised a somewhat clandestine operation to remove up to five of the boulders. Four of them now sit at the Stanley Street entrance to the Domain and another sits beside Auckland University at the top of Wellesley Street. Another one now sits on the corner of Tamariki Street in Orewa township.

Left: Four concretion boulders sit in a park setting at the Auckland Domain entrance. To the credit of the Auckland City Council, the boulders are being accorded the kind of respect they deserve and an explanatory brass plaque has been placed beside the display. The plaque reads:

'These boulders, known technically as concretions, grew in porous sand below ground. Lime (CaCO) being carried in solution in ground water and precipitated between the sand grains as cement. They come from rocks about 60 million years old. These particular boulders were obtained by courtesy of the Ministry of Works from the property of Mr. A.H. Grut of Silverdale.'

Each boulder has some incising of straight lines on their surfaces. The one in the foreground is heavily incised by lines, double-lines, crossing-lines and arrow-pointers and possibly represented a map of alignments to locations in the vicinity of Silverdale. This hypotheses would need to be checked by careful analysis at the Silverdale location after a full rubbing of the boulder had been completed to record the many straight-stroke markings.

Right: Another boulder is on display at Auckland University and is also being accorded dignity as a display item. It bears faint curvilinear or stacked stroke incising on its surface, which needs to be recorded and studied to determine its significance to the ancient people who placed it there.

The author stands in front of the largest boulder still in evidence at Silverdale. Around it, smaller ones lie shattered or only partially intact. Like the other boulders, now residing in the inner-city, these Silverdale ones have ancient incising marks on them. There's a small amount of curvilinear marking, but most marks are straight strokes or arrows that have been cut through multiple layers of the outer surface of the concretions. The marks, which are sometimes very long straight lines or even parallel lines running for several feet, cannot be attributed to the scratches or scrapes of modern machinery moving the boulders, nor to the birthing marks of concretions in their formation stage. They look more like the typical "directional incising" that we encounter on, mostly, basalt boulders around New Zealand, often in very remote locations.

The surviving portion of the hillock, across the motorway, appears to be the highest spot for a considerable distance within the region. It also offers panoramic views for, virtually, 360-degrees and especially NNW and SSE. The many large boulders were found at the top surface level when the hillside was cut away. Their original location would correspond vertically to a position above the garden divider in the centre of the road. At that spot they were perfectly on the line to be the northern marker for a multi-component structure alignment that crossed the Auckland Isthmus to the Bombay Hills region, then onward through the centre of Lake Taupo to locations further south.

This impressive boulder (two flat bottomed pancake types actually, back-to-back), with a diameter of about 6 feet (close to 2 metres) sits slightly to the east of the surviving hill crown and is surrounded by a number of smaller, broken boulders. In retrospect, perhaps it was a good thing that five of these concretions boulders were taken away by the Auckland City Council 35-years ago. At least those ones are still fully intact and on display. By consequence, those left at Silverdale lie amongst construction rubbish or are deteriorating very badly because of a lack of encasing support at their bases. There doesn't seem to be any form of preservation order in place to protect the massive boulders still at Silverdale and, certainly, no effort is being expended by the local community or Rodney County Council to preserve them for future generations. These concretions found atop Silverdale hill aren't "just rocks"...they're incised artefacts that once formed a surveying structure built by the ancient Patu-paiarehe people of New Zealand. Once they're gone, a very important tangible link to our longterm history is lost with them and future generations will mourn that loss.

Left: At the Wainui Historical Society Museum is this very intricate spiral pattern incised into stone. Right: On one of the large spherical boulders the faint, weathered signs of side-to-side incising is in evidence. This pattern is not dissimilar to the incising on the large obelisk at the Bombay Hills, which incorporates the same flattened, layered, meandering, spiral design (see Section 1). Another pattern that appears to be in evidence on both far-flung sets is the "V" symbol, lying at intervals upon the Bombay Hill's obelisks or the Silverdale boulders, on various angles.

The fact that ancient incising can be positively identified to be present on both sets of far flung alignment markers, situated at opposite ends of the isthmus, negates any possibility that these obelisks or boulders emerged from the terrain, for the very first time, only recently. Both sets once stood above ground for a very long time and were objects that attracted attention or veneration, leading to the same "flattened spiral" or "V" symbols being incised into their surfaces. The Bombay Hill's obelisks are made up of hard durable basalt, some of which has patches of a softer outer layer of sedimentary ash, compressed or hardened into rock. By consequence, the Silverdale concretion boulders are composed of a limestone-sand material, which is softer and far more susceptible to weathering than basalt rock. This would account for the much fainter appearance of incising on the Silverdale boulders. Both sets of markers were, without doubt, put in place at approximately the same epoch to act as component parts of the selfsame surveying alignment, but the Silverdale set had a lesser ability to counter the abrasive actions of the natural elements.

In this montage, the top left picture shows an enhanced view of the design on the Bombay obelisk, whereas the right picture shows an enhanced view of the design on the Silverdale concretion boulder. Both are like flattened spiral or serpentile designs that curve at the sides to form the next upward layer. A very similar pattern is found on a large boulder (centre) at the east gate of Knowth in Ireland, which dates to 3150 BC. Likewise, three views are shown of an obelisk in Britain bearing "Ogham" inscriptions. It can be seen that the same flattened or layered spiral method is used to form letters of an alphabet in this form of writing. The Ogham obelisk seems to have a bas relief "V" incised into it also, which would be accentuated by bright sunlight and shadow. The Bombay obelisks show several examples of this same bas relief "V", which become very prominent in particular sun angle conditions during the day.

On the side of the same boulder that contains the five hand-hewn bullaun bowls are cleverly executed "V" configurations. Rather than simply incising the clearly seen large "V" into the stone in "bas relief", the ancient people laboriously removed a large section of stone surface to form a "V" hump, with one edge in "raised relief". This then has the effect of forming a very distinct "V" shadow at a particular sun angle, which diminishes in intensity or even disappears as the sun moves to other angles throughout the day. This boulder has several examples of the raised relief "V", facing various directions. They, undoubtedly had a function to "tell the time", either during the day or during the year, by the type of shadow they cast. During the year the sun moves from its Winter Solstice position to its Summer Solstice position. This annual oscillation, up and down the horizon, with the Equinox position at the centre point, extends over 60-degrees of horizon arc for Auckland, New Zealand. An adept reader of the shadows cast could tell both the time of day and the exact time of year, with excellent relative accuracy, by the observable changing shadows cast. One of the several types of "V" designs executed seems to be: one stroke of the "V" is bas relief incised into the surface and the other stroke is raised relief, creating one trough shadow and one straight edge that casts a shadow onto a lower flat surface. In the photo above, one can see at least four of the "V" symbols, adorning the same boulder. Other obelisks in the cluster also carry the "V" symbol.

1. This is an "X" formed by incised crossing lines. It also has an arrow pointer crossing it on the diagonal.

2. This is a set of parallel lines with faint lines branching off them. The design is reminiscent of Ogham writing.

3. This is a very long arrow, extending for several feet over a boulder, suggesting a direction to some location. One heavily incised boulder at Stanley Street, in particular, seems to display all of the attributes of a map.


Surveying is an exact science, wherein it's pretty much impossible to fudge the results to any degree (pun intended). When doing long-distance overland surveying using a handheld GPS to provide the fixes, it's left up to swirling and whirling satellites high overhead to provide the cold, hard and clinical coordinate numbers. After getting the location fix via triangulation's provided by up to twelve satellites, the values are transferred into the architectural program, AutoCAD and end up as precisely distanced and angled dots across a computer screen. In the entire process, human participation is reduced to simply providing the finger that pushes the GPS unit's button or taps the coordinate numbers derived therefrom into let's add to the story:

Once upon a time the Silverdale boulders were removed, probably from their watery home in the Wade River or channel of the Orewa River and hauled, at great effort on the part of the Patu-paiarehe, to the elevated inland hillock just north of Silverdale. The huge boulders were positioned very precisely to form a massive, highly visible target that constituted the northern leg or trig in an alignment that, otherwise, ran southward from Mt. Wellington to Totara Park in Manurewa, before going to Puketutu Hill, just beyond the Bombay Hills. All in all, the very accurate alignment across the Auckland Isthmus ran for 44.1-miles (almost 71-kilometres). The boulder trig to the north at Silverdale and Puketutu Hill trig to the south at Bombay, were each situated almost equidistant from the centre position of Mt. Wellington. Let's see what this looked like:

Starting from the north at the Silverdale boulders, the line crosses the high ground at Okura and there is another mound marker there, perfectly located on the ridgeline. The line then runs down the coastline, brushing between North Head and Mt. Victoria in Devonport, before crossing the ancient trig mound on Mt. Wellington. It then proceeds over the large mound at Totara Park in Manurewa before resolving on the highest point of Mt. William (Puketutu).

The north-south alignment traverses the east-west equinox alignment extending from Stockade Hill, through the crest trench at Mt. Wellington and onward to the marker stone boulder atop Mt. Albert. The alignment from Silverdale to Bombay also traverses another (true north-south) alignment that extends from an obelisk site at Papakura to the obelisk cluster on Mr, Kevin Plummer's farm at Bombay. It can be safely predicted that there would have been many interim markers along the 44-mile alignment through Auckland and we might yet be able to detect a few more that have survived.

Gene stands atop the ridgeline mound in the high forest at Okura. It took about an hour to walk to this location from the last driveable forestry road into the area. The exact coordinates of where the Okura ridgeline mound "had to be" were calculated in AutoCad, in conjunction with Tumonz mapping program, and an expedition was mounted to see if the ancient Patu-paiarehe had placed an alignment marker at that location. Rising above the high ridgeline near the modern trig tower and situated to the south side of the present track, there is a voluminous earth heap forming a very "out of place" hump. It is exactly where it needs to be and is, undoubtedly, the remains of a very ancient surveying marker mound, located between the Silverdale boulders and the trig mound atop Mt. Wellington. We found no surviving stonework on the Okura mound.