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psammite Min.|ˈpsæmaɪt, ˈsæmaɪt|
[a. F. psammite, f. Gr. ψάµµος sand + -ite: cf. Gr. ψαµµίτης sandy.]
Orig., a fine or smooth-grained sandstone: see quot. 1859. In later use, a sediment or sedimentary rock composed of medium-sized particles (now commonly defined to be between 1/16 mm and either 2 or 4 mm diameter); also, a metamorphic derivative of a sandstone.
1837J. T. Smith tr. Vicat's Mortars Pref. 9 Other words, used for the purpose of defining substances hitherto classed by us under a more general category..such as ‘arenes’, ‘psammites’, &c., I have thought it advisable to convert at once into English terms. Ibid. App. 178 The species of sandstone called grey-wackes by the Germans, and psammites by M. Brogniard. 1859Page Handbk. Geol. Terms, Psammite,..a term in common use among Continental geologists for fine-grained, fissile, clayey sandstones, in contradistinction to those which are more siliceous and gritty. 1879Rutley Study Rocks xiv. 299. 1882 A. Geikie Text-bk. Geol. 154 (heading) Gravel and sand rocks (psammites). 1933Geogr. Jrnl. LXXXI. 158 If the water table approaches the surface evaporation takes place, causing a concentration of the salts carried down. These salt-sand crusts are psammites. 1962Read & Watson Introd. Geol. I. v. 260 (heading) The psammites: sand, sandstone, greywacke, arkose. 1977A. Hallam Planet Earth 174 Meta-sandstones are sometimes called psammites.
Hence psammitic |-ˈmɪtɪk| a., pertaining to, containing, or of the nature of psammite; consisting, as a sandstone, of fine rounded grains; also, derived by metamorphism from a sandstone.
1847in Webster. 1879[see psephitic]. 1882A. Geikie Text-bk. Geol. 87 Psammitic, or sandstone-like, composed of rounded grains, as in ordinary sandstone: when the grains are larger (often sharp and somewhat angular) the rock is gritty, or a grit. 1910Q. Jrnl. Geol. Soc. LXVI. 377 They may be conveniently divided into (1) a Psammitic Group, consisting chiefly of flaggy quartz-felspar granulites..; and (2) a Pelitic Group, consisting chiefly of garnetiferous mica-schists (or gneisses) which are often coarse and quartzose. 1921G. W. Tyrrell in Geol. Mag. LVIII. 501 It is suggested that the terms psammitic and pelitic might usefully be restricted to the hard metamorphic rocks which have been changed beyond the limits implied by the corresponding Latin terms [sc. arenaceous and argillaceous]. 1956E. W. Heinrich Microsc. Petrogr. iv. 99 Psammitic and pelitic rocks may be further subdivided on the basis of mineralogical composition. 1959Trans. R. Soc. Edin. LXIII. 554 In a series of psammitic and slightly calcareous pelitic schists, such as those of Morar, there is great difficulty in discovering the metamorphic grade in relation to that of other areas. 1962Read & Watson Introd. Geol. I. ix. 539 Psammitic gneisses commonly form massive pinkish rocks composed principally of quartz and feldspar. |
