Monday, May 24, 2010

Ground Slate Lances

Ground slate lances with sandstone and metal tools
Ground slate projectile points show up in the archaeological record in Newfoundland and Labrador fairly frequently.  They are found in Palaeoeskimo, Maritime Archaic Indian, and Inuit sites.  In Palaeoeskimo and Inuit sites, ground slate points tend to be small, and likely tipped harpoon heads.  The Maritime Archaic Indians made larger lances and bayonets, that likely tipped longer spears, but as with the harpoon endblades, they were still marine hunting tools.  Lances were flat, like the reproductions in the photos in this post, while the bayonets are narrower, with a triangular cross-section.

Pile of slate
Slate is easy to work.  It splits apart into flat sheets along natural cleavage planes, so setting the thickness is as simple as finding a piece of slate that's already the right thickness for your project.  Its a popular building stone so even if you can't find the stone in nature, you can buy floor tiles or roofing slate that are already nice and thin.  You can roughly trim it into shape using a hammerstone, but it doesn't flake the way chert or flint does and there is a tendency for edge work to carry cracks along cleavage planes into the middle of the stone and unintentionally split the piece in two.  So I'll usually just saw it.  You can use handsaws, but the stone dulls the blade fairly quickly, so I'll use an angle grinder with a masonry or diamond blade.
Slate lances and wet grinding wheel

I have a wet grinding wheel that I use for rough shaping.  Its the same idea as grinding the slate against a sandstone abrader, but uses an electric motor instead of muscle power to operate.   The wheel has a pretty fine grit and it doesn't grind stone all that much faster than manually grinding with sandstone or metal tools, but I find it a little easier on my back and hands.  The biggest drawback is the shape of the wheel - the round surface will leave little dimples all over the flat surface.  I like to finish the lances with wood rasps and metal files, to leave clean, flat surfaces.  Sandstone abraders work as well.  The final polish is accomplished with sandpaper, oil, and rubbing with a leather cloth.

Slate lances from Port au Choix
The original artifacts were most likely designed for piercing the thick blubber layers of marine mammals.  Slate is a very widely available stone and ground slate points are relatively quick and easy to make, but in North America they are extremely rare point types, except on coastal sites.  Slate is softer and more easily damaged than chert points, but can be worked into a long straight, smooth edge. 

Straight slate edge vs. serrated chert edge
A knapped blade will always have a slightly serrated, steak-knife edge, while a slate blade can have the long clean edge of a filleting knife.  Terrestrial game animals, like a deer, are lean and bony, with dense meat and tissue.  Marine game, like seals or fish, will have thick layers of blubber, soft or porous bones, and more flakey muscle.  I used to imagine that seal muscle would be much denser than its fat layer and probably stop most projectiles, but while cleaning the seal bones a couple weeks ago, I was surprised by how flakey it was and how easily it pulled apart.  It really wouldn't offer much resistance to a slate lance.  You could plunge a slate lance a long way into almost any part of a marine mammal before you find a bone that would damage your blade. 

I'd be curious to hear from anyone who knows of slate points from sites belonging to cultures who didn't use marine or coastal resources.

Photo Credits:
1-3,5: Tim Rast
4: From Museum Notes - The Maritime Archaic Tradition


  1. Hi, nice slate points. Slate has been widely used in Finland during the meso- and neolithic. Slate has been used for knives, wood-working tools, arrow- and spearheads. Seals and such were hunted but apparently the harpoons used for this were only made of bone or antler. There is actually an interesting arrowhead design from the so called "Pyheensilta" phase that precedes the bronze age. These arrowheads are thin and rombic in the cross-section. Their lenght varies from 13-5cm. It appears that the arrowheads were made as long as possible. As they were used and sometimes hit the bones of prey animals the tips would crush. These arrowheads are easy to re-sharpen even if they remain on the shaft. So slate has been widely used for other than sea mammal hunting.

  2. Thanks Marcus, that's interesting I didn't know about the Pyheensilta arrowheads. I've seen some really fascinating parallels in material culture between the Maritime Archaic period in Newfoundland and Labrador and the Neolithic in your part of the world. But I don't think I've seen any slate arrowheads here. (Although the bow and arrow doesn't seem to have been used at all during the Archaic here.)

    Slate certainly is easy to resharpen, so I like the idea of exploiting that property in the arrowheads design. Were chipped stone arrowheads also made during the Pyheensilta phase? Is it reindeer that they were used to hunt?

  3. Yes, i have a book on Newfoundlad prehistory (don´t ask me how I got it) and I find that many of the objects pictured in it look pretty much the same as Finnish objects. Chipped flint arrowheads where in use until the bronze age, but because flint does not occur in Finland prehistoric people also relied heavily on quartz and slate as flint had to be imported. Flint was imported from the Baltic, Russia and from southern Sweden. Here are few pictures of typical Finnish flint arrowheads.

    Here is a photo of some Pyheensilta arrowheads, they are the long slim ones.

    Here is a picture of some artifact that are considered as "slate knives". These are dated from 4000-2000bc.

    As to what game was taken by Pyheensilta hunters it is probable that Forest reindeer, which once was abundant in Finland, was a substantial food source. Moose was also a large prey animal and a staple food source during the whole Mesolithic and Neolithic periods. I made an arrow tipped with a large pyheensilta arrowhead and found that it was worked fine, expet that the range was effected by the weight of the arrowhead. This lead me to think that Pyheensilta hunters probably hunted from blinds besides game-trails and managed to come fairly close to game animals so as the weight of the arrow would not become a problem. This type of hunting works well forest reindeer as the animal is predictable and frequently uses the same trails.


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