They do however have an abundance of Minerals, Metals, Salts, Acids, Alkalines, etc. they have access to.
Cool.
One thing that you'll soon learn in any good school's chemistry lab is that you should not ❤❤❤❤ with alkali metals. If you have a sample of sodium or potassium you will generally keep it inside a container that is filled with oil, because these ❤❤❤❤s will catch fire if exposed to air humidity. Depending on your setting, they might even explode. They will explode in contact with liquid water:
Sodium spontaneously explodes in the presence of water due to the formation of hydrogen (highly explosive) and sodium hydroxide (which dissolves in the water, liberating more surface).
A small block of sodium can even cause a toilet to crack, and you will probably get a detention by doing that.
Anyway, these elements are so reactive that on Earth, you practically cannot find them in their pure forms outside a lab. Your crystal aliens will probably not be able to find pure sodium as well, but if they have developed chemistry, they may be able to separate it from other elements. If they do, you've got a way to make rocket fuel. Just add water:
$$ 2H_{2}O + 2Na \rightarrow 2NaOH + H_{2} + heat $$
That reaction is exothermic, so you can capture the energy it releases for other processes. The best part is that H2 is a proper, tested-and-used rocket fuel on Earth. It's what propels the space shuttle. Just add oxygen (careful, this is highly explosive):
$$ 2H_{2} + O_{2} \rightarrow 2H_{2}O + boom $$
The huge amounts of energy heat the water into a gas or plasma which shoots out of a rocket's engine as exhaust gases, pushing the ship forward.
Since your lifeforms are crystaline, their rockets would probably need much less life support than those developed by humans. Supposing they have at least the same level of metallurgy as we do, their ships would be much lighter. Tell you what, if your aliens have radio and computers, they will probably be much better at space exploration and colonization than us.
They will need to develop metallurgy, though. Steel does not occur naturally, and crystals are not known for their blast resistance (i.e.: bad for combustion engines).