How do you identify a metamorphic rock in a field?

How do you identify a metamorphic rock in a field?

Metamorphic rocks are rocks that have become changed by intense heat or pressure while forming. One way to tell if a rock sample is metamorphic is to see if the crystals within it are arranged in bands. Examples of metamorphic rocks are marble, schist, gneiss, and slate.

What is a description of a metamorphic rock?

Metamorphic rocks were once igneous or sedimentary rocks, but have been changed (metamorphosed) as a result of intense heat and/or pressure within the Earth’s crust. They are crystalline and often have a “squashed” (foliated or banded) texture.

What are the typical metamorphic rocks in the field?

Common metamorphic rocks include phyllite, schist, gneiss, quartzite and marble. Foliated Metamorphic Rocks: Some kinds of metamorphic rocks — granite gneiss and biotite schist are two examples — are strongly banded or foliated.

How would you describe rocks in the field?

The general process for writing rock descriptions is to start off with a general description (general colour, grain size, texture..) , followed by identification of the minerals within the rock (the mineral assemblage), the name of the rock (deduced from the assemblage) and then finally your best guess on how and where …

How do you classify metamorphic rocks?

Metamorphic rocks are broadly classified as foliated or non-foliated. Non-foliated metamorphic rocks do not have aligned mineral crystals. Non-foliated rocks form when pressure is uniform, or near the surface where pressure is very low.

How would you describe rocks in hand specimen?

Basically, hand specimen descriptions should tell someone looking at a rock everything they need to know to recognize it in the field. Descriptions should be reasonably comprehensive but clear and succinct, typically no more than two sentences. half alkali feldspar and half plagioclase, call the rock a granite.

How do you describe the texture of a rock?

The texture of a rock is the size, shape, and arrangement of the grains (for sedimentary rocks) or crystals (for igneous and metamorphic rocks). Also of importance are the rock’s extent of homogeneity (i.e., uniformity of composition throughout) and the degree of isotropy.

What are the three classifications of metamorphic rock?

How does a metamorphic rock form from a parent rock?

Metamorphic rocks form from pre-existing rocks (“parent rocks”) due to changes in either temperature, pressure, or volatiles within the earth, often by a combination of all three.

Which is an example of a foliated metamorphic rock?

Foliated textures are further described on the basis of the grain (crystal) size in the rock. Examples of complete descriptions of foliated metamorphic rocks include: foliated, nonlayered, very fine grained for slate, foliated, layered, coarse grained for gneiss, and foliated, nonlayered, fine grained for phyllite.

Which is the best description of contact metamorphism?

Some rocks, such as limestone are made of minerals that are not flat or elongate. No matter how much pressure you apply, the grains will not align! Another type of metamorphism, contact metamorphism, occurs when hot igneous rock intrudes into some pre-existing rock.

Where are metamorphic rocks found in the Cobalt Belt?

USGS scientist Art Bookstrom looks at puzzling sedimentary structures in metasedimentary rocks of the Apple Creek Formation, near the Jackass prospect, near Iron Creek, in the southeastern part of the Idaho cobalt belt, in east-central Idaho. Intensely fractured Proterozoic metamorphic basement rock exposed in Poncha Canyon.