Correct, gaara's dad manipulates sand via magnet release. What is interesting and something I dont understand is that when actively manipulating gold dust gaaras dad displays the same characteristic dark rings around his eyes as gaara. It was assumed that gaaras rings are from lack of sleep but they still haven't disappeared since shukaku was extracted. This could suggest gaara has some sort of always active field that he taps into to manipulate the sand, but who knows.
But still 3 of the 5 kazekage have shown an ability to manipulate a form of earth mineral as the one sasori killed had iron sand. So it's not that surprising that gaara can do it too.....still not quite sure whether some form of magnet released is used though.