Obsidian is not particularly hard (unlike diamond), itвЂ™s just capable of being very sharp.

So why arenвЂ™t we all equipping our kitchens with obsidian knives? Obsidian knives are quite delicate and tend to be a little brittle, so theyвЂ™re probably not your best choice for the rough and tumble of a kitchen, particularly where they might strike something hard. Since obsidian will fracture down to a single atom, it is claimed to have a cutting edge five hundred times sharper than the sharpest steel blade, and under a high magnification microscope an obsidian blade still appears smooth, whereas a steel blade has a saw like edge. The Mayan Indians are credited with using obsidian blades first 2,500 years ago, although Stone Age spear tips made of obsidian have been found elsewhere in the world. This stops it from forming a crystal structure and also introduces a form of вЂcompressive strengthвЂ™ which makes the material even stronger. Obsidian is a volcanic glass that is created when magma is pushed to the earthвЂ™s surface and is cooled very rapidly. Glass on the other hand is вЂamorphousвЂ™, so it does not have any natural planes to split, or cleave to, making it much more suitable for making sharp edges.ДЄ type of naturally occurring glass that has already been in use since the Stone Age as a blade is obsidian. The difficulty is that diamond crystals tend to вЂcleaveвЂ™ in whatвЂ™s called an octahedral fashion, which doesnвЂ™t allow for a very sharp blade cross-section. The hardest material out there is diamond, so logically a diamond knife should be the sharpest type. So there is an element of practicality as well. The trade off, of course, as weвЂ™ve mentioned already in our article about Samurai swords, is that very sharp blades can be very brittle, and itвЂ™s no use to anyone if parts of a knife break off while itвЂ™s being used. Leaving aside our knives of course, there are many earnest scientific discussions/arguments on the web as to which material makes, or would make the sharpest blade. Which brings us to the oft discussed topic of the sharpest blade in the world. If anyone has earned the right to be a bit nerdy about knives, then itвЂ™s us.

Obsidian knife