What kind of gravel was it, what was the pH reading, and what sort of fish do you want to keep ?
Some gravel chips, especially if they are white, may be marble. That's pure limestone, which will leach calcium into the water and keep it very hard and alkaline, which is not a problem if you plan to keep fish that like those conditions. African cichlids come to mind.
You can test any rock you might wish to use, any gravel and even the sand as well, to find out if it has a lot of calcium in it. Either get some hot pickling vinegar [ 7% acetic acid, it's better than the ordinary 5% vinegar for this] or better still, some CLR. Both rinse of cleanly in fresh water when the test is done.
Either sit the pieces to be tested in a few tablespoons of your test liquid in a shallow dish, or pour some of the test liquid over the gravel, rock or sand on a dish. If it bubbles or foams up, it has a lot of calcium in it, and will not suit a great many fish that prefer water a bit less hard and alkaline than the cichlids do.
Some rocks may only bubble here and there, indicating they have some streaks that contain calcium but not the entire rock, such rocks are usually ok to use unless you are trying to keep soft, acid water conditions.
If you get no reaction, the items are just fine for most any fish you might want to keep.
