I was trying to see if my electrical box in the ceil was attached to a stud or not.  So in the process of trying to figure it out - I knocked out a piece of plaster - and it won't be covered by the fixture.  See in the image below.  I am not sure which material to try and match this up with or even if I can - I think it is called stipling or something.  It is like wavy with some points all along the ceiling.  Any suggestions?

Also, I noticed a huge long crack running across the room that I don't think I noticed before - I was panicking thinking I might have created it by hammer the electrical box around while I was drilling holes and such.  Anyway, not much I can do about it now in any event...