Faucet loose where it meets granite

Brand of faucet or picture?

You don't mention the brand but most faucet Mfgrs have rebuild kits.

Needs to be tightened from under the sink, may need a right angle faucet wrench, they are about $10, or you can try and snug it up by hand, hope this helps?

Probably a loose fixture nut under the counter behind the sink.
Yeah ya gotta pull out everything and crawl up into the cabinet on your back and see if the nut (right up at the granite, above the hot and cold inlet pipes) is loose. If it is THEN you'll need to tighten it. Wrench, slip-joint pliers or a basin wrench. (probably basin wrench which is a specialized tool made for reaching up into tight places)

There are screws that come up through the bottom. You may have to remove the faucet to tighten it. While you have it out, throw it away and buy a new one.

was the base installed under the faucet..is there a single hole in granite...faucets usually come with a long base to cover the holes in sink..or with one round ring for granite installation..which the faucet should be mounted on..

yes there is, with a pair of slip joints you can tighten from underneath, it is above the supply line, the best thing to do is turn off the water, disconnect the supply line and tighten the nut, then reconnect the supply line and turn back on the water. Good Luck Tim

The faucet should have come with a rubber gasket which goes between the faucet body and the granite top. Make sure it's properly aligned and has not slipped out of place. Be carefull when tightening the faucet to the granite, since granite is easily cracked.

new plumber

This is a view from the underside of our sink. Is this what you were talking about? The steel plate is W-shaped (upside down in this case) and has a single nut larger than 3/4". It's almost impossible to fit a wrench up there to tighten it.