Place magnesium flakes into a small container and add the boiling water, stirring until the magnesium dissolves. This will create a thick liquid.
Set aside to cool.
Place a quart size mason jar inside a small pan with 1 inch of water in it.
Combine the coconut oil, candelilla wax, and shea butter in the mason jar, and turn on medium heat.
When the ingredients in the mason jar are melted, remove the jar from the pan and let the mixture cool until it is room temperature and slightly opaque.
Pour the mixture into a medium bowl or into a blender.
Use a hand blender, immersion blender, or regular blender on medium speed to start blending the oil mixture.
Slowly, starting with one drop at a time, add the dissolved magnesium mixture to the oil mixture while continuing blending.
Continue until all of the magnesium is added and it is well-mixed.
Put the lotion in the refrigerator for 15 minutes.
Remove it from the refrigerator and re-blend to get body butter consistency.
If you have pre-made magnesium oil on hand, you can use ½ cup of that instead of the magnesium flakes and boiling water.
Store in the fridge for a cooling lotion (best consistency), or at room temp for up to two months.