Sand questions!

[tyler1503]

Can anyone tell me what kind of sand this is and if it's suitable for a marine tank?
It came with a second hand tank I bought recently and I believe it was a cichlid tank.
It's very crystalline making me think it may be quartz sand and is safe, but not the most appropriate choice. I'd prefer aragonite, but if this is safe, I'll save my money :)

 

[PatW]

I can't tell by looking. Sand used in aquariums should be calcium carbonate. You can take a little sand and add 10 percent HCl and the sand will fizz if it is calcium carbonate. Add enough acid and pure calcium carbonate will fizz completely away leaving no residue. If you don't want to mess with that, you could buy new sand.

 

[tyler1503]

It's definitely not calcium carbonate unfortunately. Thanks for the acid tip too! Is vinegar strong enough to get any sort of reaction?
I'm hoping someone can confirm whether or not it's quart based as I suspect it is. I read quartz sand is inert and won't leach silicates. Not sure how true that is :/

 

[PatW]

Vinegar isn't strong enough to produce a fizz.

I don't know if quartz would work. But calcium carbonate sand is pretty cheap.