I’ve been coming across videos of people breaking obsidian chunks to make arrowheads but could never find the answer why it could be broken with light hits with a rock, and then not break when in use with said weapon.
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Unless you screw up your aim, it will be hitting soft, easily slicable stuff instead of another rock. Obsidian is very good at slicing soft stuff.
Obsidian can be made very, *very* sharp; however, it’s not particularly durable. It doesn’t last long as tool but it’s very effective while it lasts.
As to why you can easily knock off a chunk to turn into a tool but not have it immediately break when you try to use: obsidian breaks in certain specific ways. If you understand what those ways are you can use it to your advantage to break off a nice, big flake. That nice, big flake will easily break if you apply pressure across it but not so easily if you apply pressure head-on. So it works pretty well for stabbing into things, not so great as like a lever or something.
It’s worth noting that it’s still used for tools today. Surgical scalpels are sometimes made of obsidian because of that sharpness. I don’t know how often those need to be replaced.
The first thing is that it is naturally occurring. This doesn’t mean much in our modern times but it was a big deal before humans had convenient access to things like forges and modern metal purification.
It is relatively easily made into a very useful sharp object. Again, this seems unimportant today but at a time when there were only primitive tools, making sharp, hard, cutting objects was not simple. Think about how a metal tool is made with no access to modern equipment. (Bronze and copper are soft metals so don’t hold an edge very well).
First you had to find the ore, then you need to build a kiln and furnace probably out of clay/hay etc. Then you have to gather wood (no metal axes) dry it and perhaps make charcoal in the kiln. Make bellows (animal skins?) to get a hot enough fire. Make a casting mold. Then melt the ore and pour it and cool it (all with primitive tools and clay). The result is usually low quality metal. Then hand grinding it on rocks, likely, to even get an edge.
Of course, all this while, there is no supermarket to feed you. So you’re also going to ensure you have someone provide you with food or hunt food in the meantime.
No one is making swords out of obsidian or even spear tips. They’re making arrowheads out of obsidian because it can be made insanely sharp with very little work. What does it matter if an arrowhead shatters after it penetrates 4″ into your victim’s chest?
Obsidian can be made very, very sharp, by breaking it along particular lines. They can even be made sharper than metal blades, and hold that edge better, and surgeons used to prefer obsidian scalpels for that reason. But they’re very hard to sterilize, which is why you don’t typically see them in medical settings anymore.
This sharpness, though, has made obsidian very desirable for use in cutting tools since ancient times. Arrowheads were especially popular, because the arrowhead isn’t expected to last for more than one use anyway: fragility isn’t a problem if the arrow can break through the target’s skin once, and arrowheads can manage that. Fighting knives are more iffy, because the high forces involved in fighting can break a blade easily, but they did see use in small utility knives that didn’t need to stand up to those kinds of forces. Obsidian razors for shaving have also been historically popular. Mesoamerican civilizations had the *macahuitl*, a kind of cross between a club and a sword with slots to hold replaceable obsidian blades. This helped mitigate obaidian’s fragility by slotting it into a more durable backing: if a blade breaks, you just put another one in, and even if you can’t do that right away, the weapon still mostly works.
But it basically all comes down to obsidian’s unmatched sharpness. Even today we haven’t made anything with a sharper edge. Dust from working with obsidian is actually quite dangerous, because the fragments can cut your skin in ways most kinds of rock dust just *don’t*. And people want to use tools with that kind of edge. Obsidian’s fragility is a problem, just as you say, but for some tools, it’s worth putting up with that.
Obsidian is a type of glass. It can break with light hits because you’re hitting glass with a rock. Then you put it on an arrowhead because broken glass is sharp, and after you’ve shot someone with it, you don’t really care if you’ll get a chance to use that arrow again.
It’s incredibly easy to work with no industrialization of any kind. Metal requires smelting and forging. Stone requires time consuming grinding. Obsidian flakes off with a quick strike of a rock or antler.
Additionally, it’s convenient. You can haul around a chunk and flake off bits as needed for arrows, a quick knife, chisel, etc. This also means you can repair your club-sword after battle!
Because it can be made very sharp and very easily. It’s a trade-off. I bet I could make a sharper knife with obsidian than you could by sharpening a dull knife. It doesn’t last long, but for an arrowhead or a single opponent, it doesn’t have to. It just needs to get the job done. If you need something that last longer and you don’t have access to metal, you use stone, which isn’t nearly as good.
1st it wasn’t. It was used mainly for arrows. Occasionally spears. in some places a bladed club. There were lots of obsidian knives, but mostly for utility purposes.
Yes it’s fragile, but it’s really really sharp. Sharper than any steel blade you can buy today. It’s also easy to chip into a point or edge if you know what you are doing.
Generally though it’s simply that it was the best material they had. Steel is extremely hard to make. Iron is hard to make and doesn’t keep an edge well. Bronze, and cooper don’t make very sharp or durable edged weapons. Also it’s a lot of work to make a bronze weapon from scratch. For primitive societies their options were obsidian, flint, bone, and wood. None of which are as easy to work as obsidian or as sharp.
If you have ready access to obsidian it’s easier to make a bunch of obsidian arrows heads than other options. A flint arrow that misses a game animal is likely to be lost, and an arrow you put into a foe you are unlikely to get back. If you do recover the arrow there is a good chance the head is damaged any way no matter what it’s made of.
Although the reality is most primitive societies used what they had access to. If they had obsidian or flint they used that if not they made do with wood or bone.
Related note – I used to think obsidian was rare, until I visited this massive obsidian floe in Oregon, now it makes sense why it was so widely used: [https://imgur.com/a/yoytZrh](https://imgur.com/a/yoytZrh)
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