Min. Also 8 leucit. [a. G. leucit (A. G. Werner, 1791), f. Gr. λευκός white: see -ITE.] Silicate of aluminium and potassium, usually found in glassy trapezohedrons, occurring in volcanic rocks, esp. in lavas from Vesuvius.
1799. Med. Jrnl., I. 300. In the decomposition of the fossil, called leucit, he [Klaproth] found from 20 to 22 parts of potass in the hundred.
1800. Henry, Epit. Chem. (1808), 363. The volcanic leucite contained less potash than other kinds.
1876. Page, Adv. Text-bk. Geol., vii. 146. Many of the older lavas yield agates … leucite … and other precious minerals.
attrib. 1878. Lawrence, trans. Cotta’s Rocks Class., 135. Leucite rock may be regarded as a dolerite, in which the labradorite is replaced by leucite.
Hence Leucitic a., containing or of the nature of leucite. Leucitoid (Crystallogr.), the trapezohedron or tetragonal trisoctahedron; so called as being the form of the mineral leucite. Leucitophyr(e [G. (por)phyr porphyry; cf. GRANOPHYRE], ‘a dark-grayish fine-grained cellular volcanic rock consisting of augite and leucite together with some disseminated magnetic iron’ (Dana, Man. Geol., 1868).
1830. Lyell, Princ. Geol., I. 352. The foundations of the town [Pompeii] stand upon the old leucitic lava of Somma.
1879. Rutley, Study Rocks, x. 109. As in the little leucite crystals of the sperone or leucitophyr which occurs near Rome.
1880. G. F. Rodwell, in Nature, XXI. 352. The lava is very leucitic.
