Gluing a sink to Granite (http://tanbrown.org) ...

I'm hoping someone can help me out here. I'm trying to put a drop in sink onto a Granite (http://tanbrown.org) Counter (http://GialloFiorito.com) top. I realise in mounts are usually used but for my application that just wasn't possible. I'm finding that the silicone glue isn't holding the sink down onto the Granite (http://tanbrown.org) . Is there anything better I can use to try and (http://maplered.com) get it to stay?