Non-metal container as hard as possible for a magic flask?

[eyebreaker7]

I'm looking for some materials that I could make a magic flask out of that's as hard to break as possible but non-metal. It's going to be in the sun a lot so I don't want it to burn my skin when/if it touches it. It holds multiple potions that can be pored forth as the holder desires. Kinda like a Handy Haversack but for potions. Maybe up to 10 potions held at a time? Was originally thinking 20 but that seems kind of to many?
I have a small list of material hardness/HP but can't find it. It has different metals and even crystal-like material for psionic stuff.

[the_tick_rules]

The first that comes to mind is glassteel

[Doctor Despair]

Riverine (from Stormwrack) is made of force, and is explicitly unbreakable by most means.

[InvisibleBison]

If you're concerned about the flask heating up, why don't you just wrap it in cloth?

[eyebreaker7]

The funny thing is, I thought the same thing a while after I posted this. lol. But I figure that while I'm making it maybe I can make it out of something different too. But yea, clover it :)

[tiercel]

There’s always blue ice (Frostburn); strong as steel and half the weight, plus keeps your potions cold and refreshing on a hot day!