Hmmmm.... no. If you just add up the “iron” in the human body and multiply then you’d think yes. But no. Firstly- the process of getting that iron out of the blood cells is going to be a real pain. We are talking about a few atoms per blood cell. There is almost 0% change you’d be able to extract EVERY blood cell from a persons body anyway. So we already need more than 359 people. Problem 2: the iron in your blood isn’t ore. After extraction you’d have “iron sand.” It likely won’t be particularly pure- and even if it were as pure as the purest in nature- you’re going to need ALOT more than this suggests.
How much? Well... factoring in how much sand it takes to make an ingot, how much slag and waste there is in that process- and then how much slag and waste there is from ingots to sword... well... you’ll likely need about 2,500-3500 people. You’re left with... an iron sword. Not particularly a very good weapon. You can add carbon and if you are capable- apply master level techniques like forging a katana and end up with a relatively delicate but very effective weapon... or you could go for a decent grade of sword steel which would take killing more than 10x the amount you needed to get to an iron sword.
So basically... without inventing a host of technologies and mastering sciences beyond current human mastery, for almost 400 murders you could possibly create a very poor quality weapon. Theoretically. In reality though- you’d likely need many thousands of victims, each undergoing a tedious and slow process of extracting raw materials.
A katana is a weapon of war so it isn’t exactly a Faberge Egg. That said they can be quite delicate. A Diamond is very hard for example- but one solid tap in the right place will shatter a diamond. The complex folding technique used to make a Katana was developed because the Japanese didn’t have access to good iron and couldn’t make good steel. By folding the blade they could have a spine which was softer and could absorb force, transitioning to harder (higher carbon content) as you reach the blade, making for a blade that could take and keep a sharp edge but was also somewhat brittle.
The fine polish and clay marks on a Katana can easily be damaged, and traditionally katana tangs were pinned to the handles with wooden dowels which if neglected or subjected to extreme torsional movement, could snap allowing the blade to “fall out.”
Because of the softness of the spine it is subject to bending when encountering lateral impact or heavy forces. The Katana is a fine weapon. It’s curvature gives a larger useful cutting surface across a plane, it’s (commonly) high carbon blade allows it to be very sharp. Improvements and variations to the traditional standard as well as non traditional materials can overcome many of the shortcomings of the weapon.
Weights for a Katana (traditional) range all over the place (with length and other factors of course influencing this-) but 2-5lbs with 5 being on the heavy side- but one could make the blades more durable for combat by adding thickness which adds weight. Of course- with swords the period we discuss matters quite a bit as changes in society, technology, and battle change swords over the ages.
But in general the Katana was no where near a crappy weapon and no where near some legendary unstoppable blade. Most any “good” blade is going to be somewhat... particular... and perhaps delicate isn’t the best word to express that- but the Katana did require special care and special consideration in its use as a generality. The technology of the weapon for most given periods was behind that of many foreign weapons as a necessity of geography etc. Using ingenuity, effort, and expertise however- the Japanese were able to create a top notch and effective weapon suited to warfare that surpasses most works others could make given the same materials to work with.
Tl:dr- “delicate” may not be the best word next to perhaps “particular.” The overall point in context to the discussion was that the traditional katana used inferior metallurgy to produce a weapon of higher quality than a simple iron sword, while requiring less blood cells to produce than a sword made of suitable grade steel. Thusly if one wanted to create an effective weapon out of blood cells and be even remotely pragmatic in the number of victims- Katana would be far better than pig iron sword, and require not much more blood but much more work and expertise, and a quality steel weapon would take more victims than many wars.
Lol. I think that’s probably going to be the best investment for your efforts most likely. See? That’s solid engineering. “The customer wants it to float in the air and cost $5. Magnets? Antigravity? What do you have for me?”
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“Here is a string.”
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“Here is a string.”