Quiz: Remember the definition of mal de mer?
any member of a series of silicate minerals that consist of calcium silicates of aluminum and magnesium; gehlenite is the aluminous end-member and akermanite the magnesian end-member. These minerals crystallize from calcium-rich, alkaline magmas and from many artificial melts and blast-furnace slags. They occur in thermally metamorphosed limestones at contact zones and in impure carbonate rocks altered to feldspathoidal rocks by basic magmas. For chemical formulas and detailed physical properties, see silicate mineral (table)