Random I know but my DD grew one of the crystal growing sets (unsuccessfully I might add) around Christmas time and it spilt out of the cup and has stained a marble work top. It was a fluorite crystal and the liquid kind of spilled out and spread. We are renting the flat and are pretty keen to get the stain up but can't get anything to work. Does anyone have any ideas?! Pic attached, it's the big light white stain.