On tilleyite and its associated minerals from Carlingford, Ireland (With Plates XI and XII.)

Abstract
The mineral tilleyite was first discovered by Larsen and Dunham in thermally metamorphosed limestones from the contact zone at Crestmore, California. It is associated there with merwinite, wollastonite, spurrite, and gehlenite, and the rock is traversed by streaks of idocrase with grossular. The amount of tilleyite in these rocks was apparently small, but in certain thermally metamorphosed limestones from Carlingford it is abundant and some specimens are practically pure tilleyite-rocks, it has been possible, therefore, to make a more detailed optical and chemical examination of this mineral. The tilleyite occurs as subidioblastic crystals when abundant, or as rounded grains in calcite-rich rocks, or as irregular plates.