The best magnesium chloride I've taken orally is Dr. Carolyn Dean's ReMag. To date, it is the only product that raised my RBC magnesium, at all. The only reason I don't still use it is my body has trouble processing all the chloride. On this link she mentions the source for her magnesium; page down about 5 times. But that doesn't really address how the magnesium+chloride comes together.