I previously purchased a VIGO glass vessel sink when we replaced our countertops several years ago, and loved it.  Unfortunately, it got an ugly calcium buildup around the stopper and I tried everything to get it clean again.  I finally gave up, and purchased a new Amber Sunset Glass Round Vessel sink.  Installed it today, and it looks great.  Now all I need to figure out is how to keep the buildup from occurring again.  Strange too, since we have soft water.