Epsom Salts browning when dehydrating - burning or normal?

[R_Rose]

I heated epsom salts in the oven at 450F to make some make-shift desiccants and it went from white (some even clearish) crystals to solid white powder (caked together) with the edges turning a light shade of brown and a deeper brown at the 4 corners of the pan.

Can this damage the MgSO4, is this impurities or what? Is it over-heating? Can it be left in the oven too long and damage the compound?

 

[Bystander]

clearish) crystals

The hydrate.

white powder (caked

Mostly anhydrous.

brown and a deeper brown

Little oven cleaner residue, soap residue, odd iron from the pan, other sources being cooked out (chromatographed) through your "column packing" in two dimensions, a layer in the pan.