Rock fines are a common base.
Sand is usually mnore available.

Either way, as long as he guarantees his work and you can get him back to fix any issues, don't let the ulcer get you! Seriously, if he says it is OK, you should be able to hold him to it, and he should be willing, with a WRITTEN warranty, to warrant all his work against heaving (within reason of course!).

Sand just locks and drains... 'fine' gravel will do the same and it's probably better. The particles are a tad larger than sand and allow water to drain faster before it gets a chance to surface freeze.
If you have a drainage problem or slow absorption, the key would be that first layer of larger stone. Hopefully he put a few inches of that stuff in... tamped, and then the fine gravel locked it tight. If it's all stamped and soaked a few times, it works great.

72, these guys are all correct. The key to your patio staying flat with your freeze thaw cycles is the material underneath the gravel he is putting down. You said he dug down a few inches and for weight this is fine but if there is clay right underneath there you probably will be in trouble but your contractor knows that also.... I think you will be fine. I'm a weekend warrior but only use fine gravel when installing pavers.... I got another one in about a month...
Thanks Dave

Ok, thanks for the reassurance - I feel better. It sounds like it will be okay, but I guess only time will tell...

As long as your installer used a deep enough base of stone, and used a fine packing stone for the top layer you should be good. At my company, we use what's called a "dirty stone" which is a mixture of course and fine gravel. We put down a level of stone and compact it. Then we put down another level and compact it again. We repeat this several times to insure the paver stones will not shift and the ground stays level. We like to use a thin layer of sand as well, then compact again. After installing the pavers, we compact one last time to help lock the blocks in place. As long as the stone is compacted you shouldn't have any problems.

Here is a link that might be useful: Paver Stone Driveway and Patio Installation Tips in New Jersey

It's hard to say from the detail of your description, but the problem isn't the sand. The last layer of sand, or fine gravel, is just providing a perfectly level base to rest the bricks on and lock them together. It usually only needs to be an inch thick for that. It's the base underneath the fine stuff that's important. If he really on dug down a few inches, instead of nine to ten, and didn't use a machine to compact the coarse stone, it won't matter what he used on top. The directions on JS Hardscapings site are pretty good, and easy to understand. Make sure you get a guarantee, so assuming he's in business in a year or two you can call him back.

I second what was said about the base. If you are in an area that has frost heave, you need 8 inches of compacted stone as a base, then an inch of sand or stone dust. The upper layer is just a bedding course. The thick stone base is what minimizes movement during times of frost and it also provides the strength.

We live in northern Montana and have been researching the paver or pritchard stone patio and all the pros here say to use the course gravel as a base. The sand is just to position and set the pavers. I think you are golden on this one!