Picking up a new 33 long, where do I buy slate for the bottom?

[Purpletotodile]

So I'm picking up a new tank/stand set tomorrow, and I'm planning on putting slate on the bottom before I start cycling the tank. Where exactly do I buy the slate? I want to be sure that the slate won't leach anything into the water. Is normal slate tile from the hardware store safe, or do I need to buy from a specialty store?

 

[Blackstar65]

Home depot sells slate tile by the box. It's 12x12

 

[Sweet Pea]

You can pretty much go into any tile or flooring store to buy slate tile as well.

 

[Bekzaloltl]

I see you asked 6 days ago, but thought id say anyway that I used old slate from a roof, I just gave it a good scrub with a basic soap, then a couple of long soakings in buckets of rainwater and popped it in. The axolotls were on a bare floor for weeks before that, they didnt appear to be bothered.
The slate floor just makes it tricky feeding worms as they try to wriggle under it!