Yes. Though, I have to say that portals have never worked for me outside of Azeroth. I can only surmise it has to do with the lack of ambient mana in space. Much of arcane magic originates from the leylines present in the ground, so...

[He could go on for ten minutes on that alone, but he won't.]

Anyway. As I was saying-- conjuring a mana crystal is a little more advanced than basic food and water, but seeing as you have such a solid grasp of magic already, I think we're allowed to skip a step.

It's all about visualization. Think of the most basic gem you can, and imagine it's big enough to fit in your hand. Think about how it feels in your palm. Think about how the light plays off the edges and inside of it. It's important to imagine a smooth and polished crystal... Arcane magic tends to be very unstable, so it will leak through any imperfections it finds.