Will a diamond break if I hit it with a hammer I was having this discussion with my friend about the hardness of diamonds. I would like to know if a diamond will break or not if hit with a hammer.
Different sources across the internet mention different things. Some say it will and some say it won't if it is real. However, Wikipedia says that it will break.
http://en.wikipedia.org/wiki/Material_properties_of_diamond
I just want to confirm if it will break.
 A: The link you provided already had enough information. Well, unlike hardness, which denotes only resistance to scratching, diamond's toughness or tenacity is only fair to good.
That is, it is easily breakable by a hammer. The toughness of diamond is about  2.0 MPa which is good compared to other gemstones, but poor compared to most engineering materials.
So if I take a  hammer and hit a hammer hard, yeah that's gonna break. Diamond is hard, I agree but it's not unbreakable.
I'll roll up a little from comments, a interesting thing: 
A normal hammer hitting at 10 km/s? That will still break every known chemically bonded material. –  Dirk Bruere
A: You're probably misled by the usual form factor of diamonds.
Let's first think about a common material that's easy to break: glass. Think about a glass window pane and a glass marble. I think you'll intuitively say that it's a lot easier to break the window. But what if you'd put the marble on a concrete floor and hit it with a hammer? You'd crush the marble.
The reason for this unintuitive behavior is that applying a force to an object generally will accelerate that object. But the atoms of an object can only transfer a very small amount of force to other atoms. If you have apply force locally and there are not enough atoms to distribute that force over, they'll break the bonds with their neighbours. If that happens on a macroscopic scale, the object breaks.
Back to diamonds. They're generally small objects and typically not made in a flat form. If you hit it, usually the forces do not need to be transferred over large distances, and they're quite possibly applied to a significant fraction of the surface of the diamond (especially since diamond is quite hard and can easily leave a diamond-shaped dent in metal). Therefore, many of the atoms are accelerated together, which makes it less likely to break.  
