A few years ago, this mineral was described as a new species by Sir David Brewster, on account of peculiar optical properties ascertained by himself, and its crystallographic characters, as determined by Mr Haidinger. Berzelius, however, inferred from the analysis of a specimen sent to him by Sir David Brewster, that it is merely a variety of chabazite, its chemical constitution appearing to be, Silica 48, Alumina 20, Lime 8.35, Magnesia 0.4, Potash 0.41, Soda 2.75, Water 19.30. But, from a subsequent explanation, it seemed probable that Berzelius had analyzed not the true levyine, but a mixture of this and chabazite, constituting the specimen which was sent. The author therefore considered it desirable to execute a new analysis of the mineral in question, which he has found to yield the following results:—