Stain on silestone black stellatr night

Hi,

 

We just had a brand (http://maplered.com) new black stellar night Counter (http://GialloFiorito.com) installed but there is a film like stain running parallel along the area where the installer connected the Counter (http://GialloFiorito.com) .  It looks as if the glue or whatever substance he used to glue the seem damaged the sileStone (http://g603.net) .  We have tried washing it off but we can not remove it. He is really a Granite (http://tanbrown.org) guy and (http://maplered.com) we think he may have used something that was inappropriate for a Material (http://g654.org) like sileStone (http://g603.net) .  Is there a way to remove it.

 

Thanks nick from NY