Uh well. I'd actually steer you at a from black sand in general. I scratched the heck out of my current tank with it.
But with sand if you don't know where it came from really I'd highly reccomend not using it. You can clean it up ok and get organics and nutrients out mostly by phosphates are harder esp with sand.
Same goes for lives rock.
If it's dry soak it in a vinegar and water over night rinse it. Dump in peroxide and rise the heck out of it. And let it dry then fill the bucket with seawater and you can start cycleing.
If it's wet just the peroxide. You can add a bout two cups of peroxide or a little more. It'll fizz and look nasty Esp the more you use. The more you use the longer it'll take to rinse and to stop the oxidizeing. Add seawater and a powerhead and let it rest a week or so and rinse again it before you use it. You can put it in the tank at this point too but I wouldn't add animals yet.
If it stinks (probably won't) after the first week it's just a mini cycle. And it means there was a LOT of crud in it. Let it finish. Rinse and add fresh seawater or add in the tank. Again wait to add livestock and test the water for ammonia.