Congratulations on finding the highest quality magnesium oil. I hope it works well for you. I am curious to know if you get good results with it.
To my knowledge, LL Magnetic Clay is a primary distributor, but they do not mine the product. Ancient Minerals magnesium products are imported from Europe. The magnesium chloride is extracted and packaged by a Dutch company. North American distributors often repackage or rebottle it. While there are other brands, Ancient Minerals uses the "Genuine Zechstein" logo to indicate authenticity of their product. Ancient Minerals is the brand Dr. Mark Sircus recommends. Dr. Sircus's Transdermal Magnesium Therapy is currently the best book to read, if you want to understand how to use magnesium chloride transdermally.