Moist Magnesium Mix?

[KenRexford]

I opened a bag of magnesium mix from bulk reef supply, and somehow it had moistened into a sort of paste at the top and a block a the bottom more like when salt gets wet. I was able to mix it with water, losing just a little bit of volume, but it was very milky. Because magnesium is an element, because magnesium chloride is a compound, I assume that it has no expiration date and that the paste should be OK once dissolved. Am I wrong? Should I ditch the batch?

 

[shwareefer]

I've never had magnesium that didn't turn into big chunks because of attracting moisture. I'm guessing it's fine.

 

[Randy Holmes-Farley]

It is chemically fine, but the potency may be hard to judge due to the water in it.

That said, it is not as simple as "Because magnesium is an element, because magnesium chloride is a compound, I assume that it has no expiration date and that the paste should be OK once dissolved."

Calcium hydroxide and Magnesium hydroxide both fit your description but it can go bad as CO2 enters it and forms insoluble carbonate salts.