noob question(chain)

I'm trying to make a necklace,but I found most necklace in SL is not like a real necklace,I mean necklace is affected by gravity force,but after I connect two ring of the necklace,it said I cant make the prim physical,how can I do that in SL?

You cannot make small, jewelry sized prims physical they will likely fall apart as the physics engine is isn't designed for simulation at that size.

The new Havok 4 physics engine is alleged to come out sometime before the heat death of the universe, but preliminary reports seem to show that it won't do much better.

Look at the jewelry out there, none is physical, all is rigid and is worn on the neck as a "belt" of sorts.

to give the 'appearance' that it isnt siumply a ring, maybe make the chain itself shaped down around the shoulders and such, and if you want to go crazy, script a little sway into it while walking

You could refer to this kind of shape as a 'saddle' shape, which you can achieve with the freebie LoopRez generator, created by Ged Larsen. It's coooooool!

Adding: also, attaching necklaces to 'chest' instead of common default 'chin' will make them move far more naturally anyway

Thank u all very much!