The thin edge of a truly sharp obsidian knife tends to be extremely brittle and can chip or break easily. This makes it unsuitable for most tasks where it will be exposed to impacts or hard use. The other major drawback is that, since obsidian is not formed under pressure like a diamond, it is not very hard or durable. Obsidian knives have to be sharpened through a process called knapping, which is essentially chipping away bits of the material until you have a sharp edge. If you have an obsidian knife, you’re not going to be giving it a few strokes on a stone or in your strop to keep the edge. The first major drawback is the work that’s required to form the super sharp edge.

However, it comes with all the drawbacks that you would expect. Like a ceramic or glass, this allows obsidian to form an extremely keen edge. Because of the speed at which it cools, it does not have time to form a crystalline structure and, instead, forms a glass. Obsidian is created when highly viscous lava is cooled rapidly. Learning about the creating of obsidian and how it is formed into a knife sounds like something straight out of a fantasy book. What I’ve learned is super cool but, I’ll admit, a little disappointing for those of us that wanted an obsidian pocket knife to carry.

Given how incredibly sharp and hard I thought obsidian was, it seemed like the perfect material. This led me down the road of obsidian knives. I recently had a bit of a romantic trip down memory lane and decided to start looking for a practical way to use obsidian. There was a site on my family’s land where we found dozens of 200+-year-old arrowheads that were still sharp enough to slice my fingers (ask me how I know…)

I’m sure the food was great, but the most exciting thing we did was look for obsidian pieces and arrowheads. Metals are hardened to make the crystallites (grains) smaller, but isn't that adding imperfections to the crystal structure? Meanwhile, the obsidian won't deform because the crystallites aren't aligned, so it will keep the sharper edge but it's more brittle and can shatter if dropped.One of my best memories as a kid is visiting family in Idaho every holiday. So the problem is due to the fact that metal is malleable, which is a result of properties of its crystalline structure. Metal can be shaped as such, but it has to be steeled periodically because it deforms. The conchoidal fractures can create an angle that's ideal for sharpness. My experience in this is based in geology, so I don't know very much about metals, but I think the issue is that it's simpler to use obsidian than steel to get an extremely sharp edge that won't deform. That's why you get conchoidal fractures, right? It's the lack of a crystal structure that allows it to break like that. Obsidian/glass is an amorphous solid, so it doesn't have any crystal lattice. I think my confusion may be because you go from talking about a perfect crystal lattice to grain size, but I'm not sure. I don't know wether it is technically possible to make a steel edge that thin yet, but the materiel allows for it. Once you try cutting something, the steel edge will bend, and become less sharp. At that thickness, the steel blade's serration's (the ones I mentioned earlier) are too weak, and will bend once you try to use that edge. At molecular width, it's edge is hard enough to maintain that razor edge. Obsidian is much, much harder than steel. Steel can theoretically be honed until its edge is just a single molecule wide like obsidian, but here the limitations of the metal come in to play. Steel can be honed to make that cutting edge thinner, and thus, sharper. When you sharpen a knife, you are aligning the serrations to the plane of the edge. Those points will bend to either side of the blade through use,dulling the edge. Steel, on the other hand, is jagged on the edge, forming tiny tooth-like serrations on the cutting edge. Freshly broken pieces of obsidian make perfect, smooth edges that are only a molecule wide at their apex.

Obsidian scalpel so sharp no bleeding