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The description and classification of rocks.

pe·trog′ra·pher n.
pet′ro·graph′ic (pĕt′rə-grăf′ĭk), pet′ro·graph′i·cal (-ĭ-kəl) adj.
pet′ro·graph′i·cal·ly adv.


(Geological Science) the branch of petrology concerned with the description and classification of rocks. Abbreviation: petrog
peˈtrographer n
petrographic, ˌpetroˈgraphical adj
ˌpetroˈgraphically adv


(pɪˈtrɒg rə fi)

the branch of petrology dealing with the description and classification of rocks, esp. by microscopic examination.
[1645–55; < New Latin petrographia. See petro-1, -graphy]
pe•trog′ra•pher, n.
pet•ro•graph•ic (ˌpɛ trəˈgræf ɪk) pet`ro•graph′i•cal, adj.
pet`ro•graph′i•cal•ly, adv.


the branch of geology that describes and classifies rocks, usually after microscopic study. Cf. lithology. — petrographer, n.petrographic, petrographical, adj.
See also: Geology


The description and classification of rocks.
References in periodicals archive ?
Petrographically, the dominating thick finely laminated uniform siliceous-carbonate mudstone (MS) oil shale intercalates with variable intervals of grain-bearing oil shale, in which interbeds of proper mudstone alternate with laminae, lenses and thin interbeds of wackestone (WS).
Petrographically, the Lower Angeles corresponds with a vesicular andesitic-basaltic lava, with a hypocristalline porphyritic to glomeroporphyritic texture, with phenocrystals of plagioclase, clinopyroxene, orthopiroxene, olivine and opaque crystals.
Petrographically, these rocks vary from actinolite schists to epidote-bearing actinolite schists, quartz-actinolite schists, epidote-bearing quartz-actinolite schists and epidote-bearing tremolite-actinolite schists.
The body is occupied by petrographically uniform granite composed of perthite, albitic plagioclase, quartz, and small quantities of biotite, opaque oxide and titanite.
Petrographically identical samples of so-called "Silasia granite" were medium-grained biotite granite with allotriomorphic grains (quartz, feldspar) with the exception of biotite (hypidiomorphic) and directionless structure.
In this study 20 carbonate samples of Late Ladinian age, located between meters 40 and 120 of the section of Figure 2, representing tidal flat to offshore transition zone environments, have been characterised petrographically.
They included the western (granitic) pluton in the Creignish Hills pluton, to which it is petrographically similar, and inferred a similar ca.
Six soil profiles from four petrographically different areas in south-west Germany, a region characterised by a humid-temperate climate, were selected for the first runs of the new sequential extraction procedure, both to evaluate the method and to quantify the different Si-pools in the soil profiles.
Petrographically the section was discriminated between accretionary lapilli tuffs, fine hyaloclastite tuffs and mudstones cycles.
Petrographically, this facies has about 63% quartz grains, and the remaining about 27% is fine grained matrix.