BARYTOCALCITE, a rare mineral found only in the neighbourhood of Alston, in Cumberland, where it occurs as diverging groups of white transparent crystals in veins of lead ore. The crystals belong to the monoclinic system and are usually prismatic or blade-shaped in habit. The hardness is 4, and the sp. gr. 3.65. Chemically, barytocalcite is a double salt of barium and 'calcium carbonates, BaCa(CO3)2, thus differing from the orthorhombic alstonite (q.v.), which is an isomorphous mixture of the two carbonates.