Kieserite
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Kieserite, or magnesium sulfate monohydrate, is a hydrous magnesium sulfate mineral with formula.
It has a vitreous luster and it is colorless, grayish-white or yellowish. Its hardness is 3.5 and crystallizes in the monoclinic crystal system.... Wikipedia
Solubility: In water
Cleavage: and, perfect
Crystal class: Prismatic (2/m); (same H-M symbol)
Crystal habit: Massive, granular; rarely as pyramidal crystals
Crystal system: Monoclinic
Dana classification: 29.6.2.1
Formula (repeating unit): MgSO4·H2O