Angstrom minerals have a particle size small enough to enter the blood stream directly, thus bypassing digestion and the digestion ills that mag can produce. This stuff is costly, but magical. Hubby and I take a TBL twice a day (you have to put it in juice or something - it tastes awful) I personally use a swig of chocolate coconut milk.
Magnesium needs potassium. They work together.
(Mix almonds and bananas, and you've got it made.)
Magnesium ascorbate....this way you get magnesium and vitamin C. I take some every day. Just take a half teaspoon 2x per day or more. Tastes good. You can take calcium ascorbate too but not as much
http://www.amazon.com/Now-Foods-Magnesium-Ascorbate-8-Ounce/dp/B000I4ANP0