Is there a way to sharpen stone weapons?

In a society with no metals whatsoever, which is therefore using stone for their weapons, can the cutting edges of those weapons be sharpened?

  • 6
    $\begingroup$ How sharp? Cellular biologists use a micro scalpel with the blade formed from a chip of flint or obsidian to slice individual cell walls. A obsidian blade can be 3nm thick. nanometer if you need to to gain perspective to how absurdly thin this is. $\endgroup$
    – Gillgamesh
    Commented Nov 16, 2022 at 13:17
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    $\begingroup$ For nanometer reference, the yellow light from a low pressure sodium lamp (like 1980s streetlights) has a wavelength of 589 nm. A human red blood cell is around 7500+ nm across. A single molecule of oleic acid (used in high school science to measure its molecule size) is just about 1 nm. $\endgroup$
    – Zeiss Ikon
    Commented Nov 16, 2022 at 13:38
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    $\begingroup$ Take a stone. Take another stone. Smash one with the other. You'll get less stone. Repeat with the correct angles. You get an edge. Humans figured it out some three million years ago. We had an entire age named after stones. Must be possible. $\endgroup$
    – VLAZ
    Commented Nov 16, 2022 at 15:57
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    $\begingroup$ Stone tools work slightly differently... stone isn't ductile, and so you don't have sharp metal edges bending/folding over. Stone does wear away like metal (though not at the same rate necessarily). But knapping also removes a great deal more material than sharpening with a whetstone or even grinding on a wheel. There might come a time where you need to sharpen, but it's probably impossible at least in a practical sense. $\endgroup$
    – John O
    Commented Nov 16, 2022 at 16:19
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    $\begingroup$ This class of questions from stone to cucumber to milk is exhaustively answered at youtube.com/playlist?list=PLIoouZjvzMWlmd4aap97yCLJQdAMWZC02 $\endgroup$ Commented Nov 17, 2022 at 12:41

4 Answers 4


Absolutely, yes.

Historically (and prehistorically), most sharp stone tools (projectile points, scrapers, knives, etc) were made from obsidian (volcanic glass which lacks a crystalline structure), cryptocrystalline silicates (cherts, such as flint), or fine grained volcanic rock (e.g. fine-grained andesite).

Generally speaking, when one wants to make a new tool, the maker will use the percussive force of a stone against a "core" of toolstone to knock a roughly tool-sized flake off of the core. The flake is then be shaped and sharpened via percussive flaking (hitting the tool blank with a rock or antler to knock off smaller flakes), and is ultimately sharpened using pressure flaking (pressing the tip of an antler or dense stick into the tool to knock off small flakes)[1]. The flaked edge can be incredibly sharp (e.g. obsidian flakes to blade whose cutting part can often be measured in atoms of thickness; ages ago, when I was actively learning to make stone tools, I sometimes shaved with obsidian flakes). This general process is called flintknapping.

As a knapped tool is used, the edge will wear (as flakes are knocked off in a non-systematic fashion). The edge can be refreshed by using the same knapping technique as is used to construct the tool in the first place.

A great reference for the practice of flintknapping is Dr John Whittaker's book Flintknapping: Making and Understanding Stone Tools (disclosure: John is a good family friend; the book was illustrated by my mother—that said, it is an authoritative text in the field).

That being said, it is likely that stone weapons will come in one of two general varieties: projectiles (like atlatl darts or arrows), and "bladed" weapons with stone blades embedded into a more durable medium (such as the Mesoamerican macuahuitl). In either case, using the weapon is likely to either leave the stone parts relatively unaffected, or to completely break them. It is unlikely that one would seek to sharpen the edges of such a weapon, and more likely that one would simply replace the stone parts (i.e. replace the obsidian blades of a macuahuitl). Stone itself is generally quite brittle, hence one would not expect to make a weapon entirely out of stone (e.g. a stone sword would likely be quite useless, Minecraft notwithstanding).

[1] It is worth noting that stone tools can be quite useful, and that, for example, it is possible to buy obsidian surgical tools.



When a flint or other stone blade becomes dull, it is sharpened by either gently chipping flakes off the edge (as was done in final shaping for shaped blades) or sometimes by rubbing the edge on another stone to wear away the dulled "points" of the natural serrations in a shaped edge and expose the unworn "throats" of the individual chips that formed the edge.

The only stone tools that can't be sharpened to original capability are flake blades -- and these are quite primitive types that are usually replaced (as a culture's knapping tradition evolves) by shaped tools that can be hafted and last better.

  • $\begingroup$ In my experience trying to grind/sharpen a piece of hard stone by rubbing it against another piece of stone takes aaaaages.But we only have granite here which is very hard and maybe there are ways to make it more effective (e.g. adding sand). $\endgroup$
    – Michael
    Commented Nov 16, 2022 at 21:11
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    $\begingroup$ @Michael Key point here is that some component of the "sharpening stone" needs to be harder than some component of the tool being sharpened. If your blade is chert/flint, and your sharpening stone is weathered granite, you're going to wear away the granite. But if the sharpening stone is another flint nodule, or unweathered granite (with its quartzite grains intact) then eventually you'll get somewhere. You might look up how the Egyptians used granite to carve and polish granite... $\endgroup$
    – Zeiss Ikon
    Commented Nov 17, 2022 at 0:28
  • $\begingroup$ @Michael yeah, it takes ages, but it works. Granite is even good in this regard: The longer it takes to sharpen, the longer it stays sharp $\endgroup$
    – Hobbamok
    Commented Nov 18, 2022 at 21:58
  • $\begingroup$ @Michael Must have beat trying to dress an animal with your teeth and fingers. $\endgroup$
    – DKNguyen
    Commented Nov 19, 2022 at 1:41

You can sharpen stone tools with sharpening stones.


sharpening axe

I like this Primitive Technology series. Here Mr. Plant makes a basalt axe head then sharpens it with progressively finer stones. It is much the same as one would do with a metal tool. In the same video he makes a chisel from mudstone (which I would not think would make a very good chisel) and proceeds to cut down a tree with it. The chisel is sharpened with grinding on other stones, just like the axe.


Never heard of obsidian blades?

Obsidian is a confusing element. It cannot be considered a mineral, because as a glass it is not crystalline, whereas minerals are. But at the same time, it is classified as a mineraloid, since it has mineral qualities, but they are too variable to be pure mineral. Get it? Me neither.

First Encounters The first-ever known historical use takes us into the Acheulean age. This age is classified through the first practices of stone tool usage. Obsidian blades were often found with the remains of Homo erectus, and it is believed that these technologies developed nearly 1.76 million years ago.

The way that obsidian fractures are so sharp, that it wouldn’t even require the tool to be sharpened into anything.

Or, similarly, never heard of flint?

Flint breaks and chips into sharp-edged pieces, making it useful for knife blades and other cutting tools. The use of flint to make stone tools dates back hundreds of thousands of years, and flint's extreme durability has made it possible to accurately date its use over this time. Flint is one of the primary materials used to define the Stone Age.

If there is still enough body remaining, you can simply chip it some more to sharpen the edge.


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