Can a magnet damage a compass? I've heard the claim before that a magnet can ruin a compass, and was about to repeat it to my son when I realized it sounds like complete nonsense.  Googling turned up such unsubstantiated and illogical answers as this one and unanswered questions as this one but nothing that sounded reasonable to me and gave a convincing explanation.  Perhaps my Google bubble is at work.
Anyway, since SE is generally very reliable, I thought this was the right place to ask, before I pass on untested nonsense to my son.  Help me break the chain of untested pseudoscience via oral tradition:  does a magnet actually do permanent damage to a compass, or just temporarily prevent it from detecting magnetic north? 
If it actually does do this, please explain how that is so.
 A: Yes a magnet can damage a compass.  
The compass needle is a ferromagnetic material.  
The degree to which a ferromagnetic material can "withstand an external magnetic field without becoming demagnetized" is referred to as its coercivity. 
Another magnet near the compass needle imposes a magnetic field upon the compass needle. It is a matter of the strength of the magnetic field imposed upon the compass needle and the coercivity of the needle material whether or not the magnetic properties of the compass needle are damaged.  
A: If the field is big enough it can physically destroy the compass needle. But that might be the least of your problems at that point
A: A magnet is made by aligning the magnetic poles of all the molecules in a magnetic material so they all point the same way.
If you have a look at how a magnet is made, traditionally 
http://www.princeton.edu/ssp/joseph-henry-project/permanent-magnet/ 
or commercially 
http://www.arnoldmagnetics.com/Magnet_Manufacturing_Process.aspx 
you will see it is made by applying a magnetic field to a magnetic material in which these molecules are able to move (either a fine powder in modern manufacturing or a ductile/malleable material). 
Equally you can reverse the process, immersing a material whose molecules are able to move (like a metal, but not most sintered magnets which are held in crystal lattice)  in a magnetic field that is not aligned with its existing field will cause the molecules to move, REMOVING the alignment and hence the existing magnetization. 
Or in other words - yes - you can even reverse the compass if you try hard enough.
Edit - i noticed a comment that the compass needle can move and hence align itself with the external magnetic field, but of course a compass has only one degree of freedom of motion and can only align itself on that axis. Many are also unable to rotate freely unless held in an upright position. 
A: I am a neodymium magnet sales for many years,in fact the magnets won't damage the compass,but it will influence the compass.
All of magnets are permanent magnets,the earliest compass is found in China and use ferrite magnet.The ferrite performance is very stable,so it can be used for more than 2 thousand years and also used in many speaker equipment. Even though the magnets in compass have a little broken,the compass also can work normally.But if you put a extra magnet close to compass，the two magnets will make a new magnetic field, originally the two single magnet exist their own magnetic filed,but they influence each other to cause a new magnetic field when the compass work wrong way, but you only should take away the magnet from compass，the compass will become normal.
