How does schist differ from phyllite

Unlike slate and phyllite, which typically only form from mudrock, schist, and especially gneiss, can form from a variety of parent rocks, including mudrock, sandstone, conglomerate, and a range of both volcanic and intrusive igneous rocks. Schist and gneiss can be named on the basis of important minerals that are present. For example a schist derived from basalt is typically rich in the mineral chlorite, so we call it chlorite schist.

One derived from shale may be a muscovite-biotite schist, or just a mica schist, or if there are garnets present it might be mica-garnet schist.

Similarly, a gneiss that originated as basalt and is dominated by amphibole, is an amphibole gneiss or, more accurately, an amphibolite. If a rock is buried to a great depth and encounters temperatures that are close to its melting point, it will partially melt.

The resulting rock, which includes both metamorphosed and igneous material, is known as a migmatite Figure 7. JPG] As already noted, the nature of the parent rock controls the types of metamorphic rocks that can form from it under differing metamorphic conditions. The kinds of rocks that can be expected to form at different metamorphic grades from various parent rocks are listed in Table 7. Some rocks, such as granite, do not change much at the lower metamorphic grades because their minerals are still stable up to several hundred degrees.

Metamorphic rocks that form under either low-pressure conditions or just confining pressure do not become foliated. In most cases, this is because they are not buried deeply, and the heat for the metamorphism comes from a body of magma that has moved into the upper part of the crust.

This is contact metamorphism. Some examples of non-foliated metamorphic rocks are marble , quartzite , and hornfels.

Marble is metamorphosed limestone. When it forms, the calcite crystals tend to grow larger, and any sedimentary textures and fossils that might have been present are destroyed. If the original limestone was pure calcite, then the marble will likely be white as in Figure 7. Quartzite is metamorphosed sandstone Figure 7.

It is dominated by quartz, and in many cases, the original quartz grains of the sandstone are welded together with additional silica. Most sandstone contains some clay minerals and may also include other minerals such as feldspar or fragments of rock, so most quartzite has some impurities with the quartz.

Basaltic Trachyandesite. Compare Rocks. Schist vs Phyllite. Schist formed by dynamic metamorphism at high temperatures and pressures that aligns the grains of mica, hornblende and other elongated minerals into thin layers. Phyllite is a metamorphic rock which is formed by regional metamorphism of argillaceous sediments since their cleavage arose due to deviatoric stress.

Banded iron for.. Compare Metamorphic Rocks » More. Schist vs Eclogite. Schist vs Migmatite. Schist vs Amphibolite. More More Compare Metamorphic Rocks. Schist vs Phyllite Characteristics Though some rocks look identical, they have certain characteristics which distinguish them from others. Metamorphic Rocks » More. More More Metamorphic Ro Metamorphic Rocks »More.

Eclogite Definition Uses Formation Properties. Talc schist contains abundant talc; it has a greasy feel, a well-developed schistosity, and a grayish-green colour. What is Porphyroblastic texture? Porphyroblastic Texture. A porphyroblast is a crystal grown during metamorphism that is significantly larger than the surrounding matrix. Porphyroblasts are commonly euhedral crystals and have often deflected the surrounding foliation.

They also are frequently associated with strain shadows. Why is gneiss banding? It is a high-grade metamorphic rock in which mineral grains recrystallized under intense heat and pressure. This alteration increased the size of the mineral grains and segregated them into bands, a transformation which made the rock and its minerals more stable in their metamorphic environment. What is porphyritic texture? Porphyritic texture is a very common texture in igneous rocks in which larger crystals phenocrysts are embedded in a fine-grained groundmass.

Porphyry is an igneous rock that contains larger crystals phenocrysts in a fine-grained groundmass. K-feldspar phenocrysts in this sample. What color is gneiss? Gneiss aesthetics While all gneiss is striped or banded, the bands can be straight, gently wavy, or chaotic.

The colors can be mostly dark, or mostly light. The stone can be black and white, or black and pink, or black and gold, or nearly any combination thereof. What is non foliated texture? Non-Foliatied Texture Non-foliated metamorphic rocks appear massive or granular without the characteristic parallel mineral grains in foliated rocks. What does gneiss look like?