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