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Quartzite can have a grainy, glassy, sandpaper-like surface. Quartzite is a hard, non-foliated metamorphic rock which was originally pure quartz sandstone. [1] [2] Sandstone is converted into quartzite through heating and pressure usually related to tectonic compression within orogenic belts.
Gneiss, a foliated metamorphic rock. Quartzite, a non-foliated metamorphic rock. Foliation in geology refers to repetitive layering in metamorphic rocks. [1] Each layer can be as thin as a sheet of paper, or over a meter in thickness. [1] The word comes from the Latin folium, meaning "leaf", and refers to the sheet-like planar structure. [1]
The older country rock is crosscut by a younger magmatic body. The nature of the intruding body depends on its composition and depth. Common examples are igneous dikes, sills, plutons, and batholiths. Depending on the composition of the magma, the intrusive body may have a complex internal structure which can provide insight into its emplacement.
Granoblastic texture is typical of quartzite, marble, charnockites and other non-foliated metamorphic rocks without porphyroblasts. Characteristics defining granoblastic texture include: grains visible to the unaided eye, sutured boundaries, and approximately equidimensional grains.
For example, when mixed sandstone and mudstone sequences are folded during very-low to low grade metamorphism, cleavage forms parallel to the fold axial plane, particularly in the clay-rich parts of the sequence. In folded alternations of sandstone and mudstone the cleavage has a fan-like arrangement, divergent in the mudstone layers and ...
This results in a banded, or foliated, rock, with the bands showing the colors of the minerals that formed them. Foliated rock often develops planes of cleavage. Slate is an example of a foliated metamorphic rock, originating from shale, and it typically shows well-developed cleavage that allows slate to be split into thin plates. [19]
In geology, texture or rock microstructure [1] refers to the relationship between the materials of which a rock is composed. [2] The broadest textural classes are crystalline (in which the components are intergrown and interlocking crystals), fragmental (in which there is an accumulation of fragments by some physical process), aphanitic (in which crystals are not visible to the unaided eye ...
Granitoids range from plagioclase-rich tonalites to alkali-rich syenites and from quartz-poor monzonites to quartz-rich quartzolites. [3] As only two of the three defining mineral groups (quartz, plagioclase, and alkali feldspar) need to be present for the rock to be called a granitoid, foid -bearing rocks, which predominantly contain feldspars ...