Gneiss

the way they are supposed to be. They aren't parallel to the normal bedding planes. Figure 41 shows what mountain shale looks like:

This is due to pressure on the shale that compresses the rock in mountainous regions There is pressure that can be so great that you will get phyllites, which is fine-grained mica or schist. Schist is any medium-grade metamorphic rock that comes from shale or mudstone, usually muscovite or biotite mica. There are various colors to these products but gray is typical.

Slate is made from fine mica, chlorite, and many other miscellaneous microscopic grains of rock. You can split it into sheets because of its layering. Both clay and shales will make slate. As slate gets acted on further, you can recrystallize everything into larger micas and rocks called phyllites. Phyllites will go on to make schists with further changes. It is used for paving and roofing as well as other construction projects.

GNEISS

Gneiss is another type of metamorphic rock that is made of coarse grains. These are made from either conglomerates or granite. Expect to see a lot of feldspar in these rocks. These are foliated as well. The foliation is not as easy to see in some of these rocks. Banded gneisses can become granified, which means that it started with micaschist and ended up with gneiss. Figure 42 is what gneiss looks like:

Figure 42.

Gneiss has the coarsest grains, which makes the banding easier to see at times. Many layers are of contrasting colors, which adds to how interesting they are. Again, with high feldspar and quartz content, these can be very interesting to see. Dark parts include amphibole and pyroxene.

There are many varieties of gneiss, including these:

• Orthogneiss comes from the metamorphosis of granite or other igneous rocks.

• Paragneiss comes from the metamorphosis of sandstone and similar rocks.

• Banded gneiss comes when more flaky minerals have conspicuous banding patterns.

• Augen gneiss comes from granite plus sedimentary rocks exposed to dynamic metamorphism.