1911 Encyclopædia Britannica/Barytocalcite
|←Barytes||1911 Encyclopædia Britannica, Volume 3
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BARYTOCALCITE, a rare mineral found only at Alston Moor in Cumberland, where it occurs as diverging groups of white transparent crystals lining cavities in the Mountain Limestone. 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. There are perfect cleavages
parallel to the prism faces inclined at an angle of 73° 6′, and a less perfect cleavage parallel to the basal plane, the angle between which and the prism faces is 77° 6′; the angles between these three cleavages thus approximate to the angles (74° 55′) between the three cleavages of calcite, and there are other points of superficial resemblance between these two minerals. Chemically, barytocalcite is a double salt of barium and calcium carbonates, BaCa(CO3)2, thus differing from the orthorhombic bromlite (q.v.) which is an isomorphous mixture of the two carbonates.
(L. J. S.)