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For example, he observed that crystals of leucite and boracite, which are cubic in external form, are always doubly refracting and optically biaxial, but with a complex internal structure; and that cubic crystals of garnet and analcite sometimes exhibit the same phenomena.

Leucite, lū′sīt, n. a whitish mineral occurring only in volcanic rocks.—adj.

Within it they found crystals of leucite already formed, showing that these are the first to grow while the melted rock is still intensely hot.

Leucite and nepheline lavas are here abundant.

It may be noted that the name of white garnet has been given to the mineral leucite, which occurs, like garnet, crystallized in icositetrahedra.