https://en.wikipedia.org/wiki/Alum
In case anyone was wondering
Yours looks like Potassium Alum (Aka Potassium Aluminum Sulfate KAl(SO4)2 to me.
https://en.wikipedia.org/wiki/Alum
In case anyone was wondering
Yours looks like Potassium Alum (Aka Potassium Aluminum Sulfate KAl(SO4)2 to me.