Petrography

Definitions

  • Webster's Revised Unabridged Dictionary
    • Petrography The art of writing on stone.
    • Petrography The scientific description of rocks; that department of science which investigates the constitution of rocks; petrology.
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Century Dictionary and Cyclopedia
    • n petrography The art of writing or inscribing on stone.
    • n petrography The study of rocks; lithology; petrology. The investigation of the minerals of which rocks are made up is called lithology, which includes not only the determination of the mineral constituents of a rock. but also the study of the changes which these constituent minerals have undergone, either during the consolidation of the rock or at a subsequent period, in the course of those changes which are denominated metamorphic (see metamorphism) —changes often complicated and difficult to decipher. While in some rocks the constituents are crystallized in large and distinctly formed individuals, so that each species can be separated and analyzed by itself without difficulty, this is ordinarily not the case. Hence by the methods formerly pursued it was often extremely difficult, if not impossible, to make out clearly of what species the rock was composed. At the present time the method of examination of a rock consists in cutting from it one or more sections sufficiently thin to be nearly transparent; these are examined with the microscope, with and without the use of polarized light; and the optical and crystallographic appearances presented are generally sufficient to give not only a correct idea of the nature of the minerals, but also of the changes which they have undergone through various stages of metamorphism. Assistance is also afforded by the method of separation in which gravity-solutions are employed. (See gravity-solution.) While most geologists writing in English use the terms lithology, petrology, and petrography as nearly synonymous, others desire to limit the meaning of the first of these to the indoor or laboratory study of rocks, and would define petrography as including their investigation both indoors and in the field.
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Chambers's Twentieth Century Dictionary
    • n Petrography the study of rocks: petrology
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Etymology

Webster's Revised Unabridged Dictionary
Petro, + -graphy,
Chambers's Twentieth Century Dictionary
L. petra—Gr. petra, rock, L. facĕre, factum, to make.

Usage

In literature:

A faint buzz above the ceiling witnessed that petrography, too, was active.
"Ann Veronica" by H. G. Wells
Contributions to Mineralogy and Petrography from the Laboratories of the Sheffield Scientific School.
"Mr. Edward Arnold's New and Popular Books, December, 1901"
The publication of this scheme may be said to mark the beginning of scientific petrography.
"Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 6" by Various
Petrography and laboratory psychology were among the new sciences fostered by the new university.
"Encyclopaedia Britannica, 11th Edition, Volume 15, Slice 4" by Various
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