The Aussie Open used to be played on grass at Kyoong <sp?> stadium till about 1987. This new surface is a synthetic compound called "Rebound Ace" made with shredded tires that's supposed to be good for defensive clay courters and an attacking players. I think my university has a similar surface. I noticed that the court has a "cushy" feel compared to regular cement hard courts and the bounces are nice and high. When it gets hot, I notice too that my shoe tends to stick more to the surface.
You might be thinking about the US Open. It originally was on grass, then switched to clay in '75, the to hard court in '78 and has been that since.