Hello, I had a medical trauma that left me magnesium deficient. I start with Ancient Minerals. Nice people GREAT marketing. But the cost was too much. Here are some facts I found after months: If itís from an old seabed or from the ocean its still magnesium. So all the wonderful marketing is just that, marketing! It comes down to refining, refining, refining, to get pure MgCl2 (really the hydrates MgCl2(H2O)x) without heavy metals or acids (most seabed mag has to knock out the acids). The Japanese have been refining nigari (99.9 to 98.5 pure food grade magnesium chloride) to a very high purity for many, many yearís. Next is saturation, how much mag can you keep in solution (pure water) before it falls out. Last comes the pH... the closer to 4 and 6 pH the better for skin absorption and less itch So if you want to save money try nigari. And make your own. Also taking MgCl2 orally is good but Magnesium Glyinate is easier on the GI. Go slow. Youíre on the right road!