Let's start by talking about just what 'gravel' is. The term seems to find a variety of definitions around the country, so before we talk about your issue, it might be useful to let you know what 'gravel' is around here in New England, then you can decide is what you have is similar.

'Gravel' is a well graded, hard, durable, and natural sand and gravel, containing no organic (loamy) soils. It's free draining, which means water will readily pass through it. And it has a natural moisture content that lends to it's ability to be compacted to a very dense and hard consistency. Now, if that's what your dealing with, what does that mean to you?

It means that if what you excavated from the hole is more organic, loamy, or silty in nature, and not completely mineral soils (like gravel), then you need something else to use as a base, and dispose of that which you 'dug out'. If what you've purchased is similar to the description above, having no stones larger than an a half inch or so, then it will make an acceptable base for your patio. The caveat here is that whatever you use, it needs to be both free-draining, and it needs to be very well compacted, preferably using a vibratory plate compactor, so that when you walk on it, pretty much nothing moves.

Sand, by itself, as a base material, does not lend itself to deep compacted layers. Look at the stuff closely, and you will see that the particles are rather rounded in nature, and even thought the particles are small, they will react to compaction much like marbles, and ultimately they can move.

In the construction industry, gravel, while capable of being readily compacted to an acceptable base, isn't what the pros will lean towards due to the inclusion of stones up to and including an inch and a half or so, and they don't want to spend the time picking them out.

So, what does the industry use? More often than not, and depending on location, paver and bluestone bases are contructed of either crushed gravel, or crushed stone, or what is called crusher-run. Crushed gravel is natural gravel that has been 'processed' to eliminate stones that are too large by crushing them, and yet not requiring a sieve to pick them out of the material. Crushed stone is just that, a by-product of a quarrying operation that is crushed and then processed through a series of sieves to separate the particles by size, eliminating any and all fine particles, and creating uniformly graded products from 1/4" crushed stone up to 6" crushed stone. Crusher-run is another by-product of a quarrying operation, where stone is crushed and processed only to insure that no particle is larger than about one inch or so, with everything after the crushing operation left in the mix.

When crushed stone is used, it is on the smaller end, 1/2" or so. Beyond that, compaction isn't an option. Crushed gravel and crusher-run can be more densely compacted as the particles within are all pretty much angular, and will fill just about all available space within the layer when compacted by machine.

Sand and stone dust are used as a setting bed, no more than 1" to 2" thick, compacted, and then screeded to level. Bluestone, flagstone, or pavers are set on top of that. The dust and the sand can be worked by hand within the area of each stone in order to achieve a level final paver or stone surface.

In your case, if you already have the gravel, it's free of large stones, you can likely use it, compact it, and place a layer of sand or dust on top as the setting bed.

The keys really are....free-draining, free of large stones, and very well compacted. The material choice to fit that bill has a number of choices.