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I love rocks.  The different planes of fracture, colours, inclusions, textures, strength…and sometimes fragility…optical properties, the way they feel in your hands….

What I also love about rocks is that they can be made into the most fantastic  stone tools, or as Simon Holdaway insists in his recent interview with Graeme Hill, artefacts. 

One of the beauties of this is that different stone types lend themselves to different tool or artefact forms, and different functions. 

A joy of this is that when you pick up a stone artefact such as a Palaeolithic hand axe or side scraper, a Mesolithic microlith, a New Zealand prehistoric adze or toki, or an obsidian blade; you can literally feel the way in which it is supposed to sit in your hand, or in a shaft. 

Even in prehistory our ancestors appear to have placed importance on ergonomic design. It is important to remembered that stone tools were literally the equivalent of our metal tools today.  They would have been used in many domestic and ‘industrial’ settings of the past…and they would need to be comfortable to use! 

In the Hill interview, the types of rocks used to bring about the design, or form as it is known in archaeology, is discussed. 

          New Zealand greywacke and argillite are fine grained, relatively homogenous and strong, whilst obsidian (which is technically a glass) is fine grained, homogenous, but brittle. 

Obsidian, when flaked, produces a blade which holds a very sharp edge, and can be used as a knife.  However, in the use of this cutting edge, the blade very quickly dulls and is liable to break depending on the force imposed on it. 

 More typical rocks seen in prehistoric adze manufacture sites in New Zealand are greywacke and argillite, which produce a ‘blunter’ edge.  However they can be hafted and used much like an axe would be today; to withstand hammer like blows, again and again.

Other rocks not touched on in the Hill interview, but used in the New Zealand stone artefact industry include,

           Greenstone or Pounamu; which is dense and strong, but again due to its crystalline structure…once its zone of weakness has been found, it will break quickly and cleanly. 

           Chert or flint, used in hand axe, microlith and drill point manufacture for instance is excellent, but with force breaks along the cutting edge. The form of the desired tool also contributes greatly to the success or failure of these tools. 

          Like argillite and greywacke these two rock types are fine grained and fairly homogenous.

What is the difference between them at a practical, tool making level?

Which stone is able to be worked in what way, and allows the person working the stone to control it during tool or artefact manufacture?

New Zealand pounamu or nephrite is rated about 6 on the Mohs scale of mineral hardness (diamond is the hardest at 10).  It is also considered very tough, and fractures conchoidally.

          But, on a practical level, when making a pounamu artefact, the density, toughness and lack of controllability during flaking makes it a difficult to work.

Because of the physical properties of pounamu, it is best, or easiest, to grind and polish the tool or artefact.  The little control over the stone during flaking, makes breakage likely. Though there are examples of flaked pounamu tools in New Zealand, such as at Oruarangi in the Hauraki. 

The end result is that while a ground and polished pounamu artefact looks beautiful, and can be used to create large artefacts, it has consumed many hours of energy.  As a result, artefacts of pounamu are interpreted as ceremonial…which contributes to its ‘specialness’. 

An interesting aside to this that I like having witnessed many examples when I worked at the Auckland Museum, is when pounamu adzes break in the making.  Instead of being able to quickly turn out a modified artefact, the original tool may be turned into a completely new artefact, such is the desire not to waste the stone   This is often evident in the hei tiki.  Along the base edge of many historic and prehistoric tiki examples, a short bevelled edge can be seen, where the pounamu was originally intended as an adze.  It broke in the making, and was changed from a adze perform to a hei tiki.

Chert or flint on the other hand have a hardness factor of about 7, but because of its physical properties, flaking is possible, and fracturing easier to control by the maker.

          A hammerstone can be used to knap or flake the core of the rock, and  because of the density, toughness and controllability of the stone, the manufacturer can achieve a finished tool this way. 

Flaking or knapping is a very satisfying process due to the precision of the blows, but there is also an immediacy in the way things happen.  Strike after strike, flakes or debautage is removed.

Chert and flint artefacts can be quickly and efficiently made, depending on the skill of the knapper.  If the tool breaks during manufacture, the stone can often be speedily modified, to produce a new tool.  Because of this property, it is a stone that is often well represented on archaeological sites as it makes up a large quantity every day ‘prehistoric’ tools used in everyday tasks…all over the world.

New Zealand’s Nelson-Marlborough Argillite, Greywackes and Basalts (namely Tahunga) have a hardness factor of about 6.5-7, and whilst technically heterogeneous, are recognised as one of New Zealand’s best sources for stone tool material through out prehistory.  Argillite in particular has the capability to produce beautiful, high polished, large adzes, with excellent working properties.  See this article in the Manawatu Standard regarding a large argillite adze find in Porirua recently.

Often used in New Zealand adze manufacture a combination of grinding/polishing and flaking techniques are used, with an added pecking or hammerdressing stage.

  1. the basic form of the adze is flaked or knapped from a core with the use of hammerstones,
  2. once this is achieved the major protuberances are pecked or hammerdressed to remove them with the use of smaller, harder, hammerstones,
  3. in the final stage, grinding and polishing is conducted to finish the tool. 

In my experience of making a small greywacke adze or toki while I was studying at Auckland University, the final stage is the most time consuming part of the process.  Using sandstone grinders, or hoangas, of varying roughness, the bevel and the cutting edge are formed, and then polished.  My result was small but excellent.  It took 2 days to create from a split Motutapu Island greywacke cobble.  Under the guide of Dante Bonica, part of the Maori Studies Dept at Auckland Museum, I used traditional methods in its manufacture…and at the end Dante hafted my c.12cm 2B adze, and cut down a small tree.  Amazing!

A Method of Connecting with the Past

I want to finish this blog on an aspect of the Hill interview that I found really interesting and supports science as a discipline based on evidence.

The interview ended with Hill and Holdaways Masters student, Kane, agreeing that by witnessing and participating in the manufacture of ancient tools using traditional techniques you could feel a connection for the past. 

Graeme felt it was about a connection with past artisans and cultures.

Kane felt a connection with the past by replicating techniques, but admitted that he was thinking about it scientifically rather than contextually.

How can this be?

Through the process of experimental archaeology, archaeologists can attempt to quantify information they are collecting through a trial and error process.  Evidence is collected from the debris or debautage collecting around the knapper, the core from which the artefact is produced, the time taken to produce the artefact, the best position the stone was held and the knapper was sitting or the ability to used the tool or artefact.

The Hill interview tells us that the angle at which the stone core is struck is important and understanding the physical properties of the stone being worked are important.  These relate to the cold hard facts of rock science, and are intrinsic in this reporters belief to the final form of the artefact or tool produced.

But I often wonder in experimental archaeological exercises how the brain is able to focus to such an extent that the artefact is viewed clinically, as a series of molecules, fracture planes and physical properties for example, rather than the image of a rock as our eyes sees it. 

Did all people in the past see the tools or artefacts in this way?

I don’t know, but it is my opinion that the context and the pure artistry of the maker should not be under-estimated… and it is very probable that Graeme’s past artisan was is in fact using science…but did not know the right words for it!

References:

          Marianne Turner  2000  The function, design and distribution of New Zealand Adzes, submitted in fulfilment of PhD Thesis, Auckland University. Online.

Please note…I have not got into the intricacies and differences between chert and flint, as this is still of some debate in science circles, also, this is not meant to be a full and complete summation of rocks and their uses in NZ…And apologies for the lack of photos…