Chalkboards are often made of slate.
There are two varieties of metamorphic rock, foliated and nonfoliated. Both are used in industry and are excellent stone choices for many projects. Foliated metamorphic rocks are slate, schist, phyllite and gneiss. The properties of these rocks make them useful in industry and design. When you have a project that you are thinking about using rock to complete, you may want to consider using foliated metamorphic rock.
Slate
Slate is metamorphosed shale. It splits into layers in the same way shale does but is denser and stronger than shale, making it strong enough to be used in industry. Most people are familiar with the dark gray slate chalkboards used in school classrooms, but other colors of slate such as reds and greens are also common. Slate is used to make decorative roofing shingles or patio and inside flooring. Fireplaces and counter tops are another common use for this stone. Crushed slate is sometimes used as decorative rock in gardens and driveways. The tops of pool tables are another use of this versatile rock.
Phyllite
Phyllite is a rock that has undergone a higher grade of metamorphism (higher temperature) than the lower grade metamorphosed slate, yet a lower grade than schist. The clay in phyllite has been morphed into mica, which along with other minerals gives the rock a lustrous sheen. It has a layered appearance that is sometimes a bit wrinkled. It is not as hard as slate and is not often used in construction as slate is. It is, however, crushed and used for road and railway construction as gravel or bedding. Its glistening sheen also makes it a good decorative rock for gardens.
Schist
Schist is an intermediate metamorphic grade foliated rock. It is visibly grainy, containing substantial amounts of mica giving it shine. It varies in color depending on what other minerals the rock contains. Schist is not as strong as some other stone used for building, as the mica can make it split easily. Some schist is used for building stone, however. Princeton University, the Philadelphia Zoo and the University of Pennsylvania are examples of places where buildings were constructed using schist. Schist is also used as a veneer stone. It is widely used as decorative stone as well.
Gneiss
Gneiss is a high metamorphic grade of foliated rock composed from granite, schist or other types of rock. It is coarse-grained rock with bands which alternate dark and light. The banded patterns sometimes swirl as if the rock had been folded. This rock is durable and is widely used as building rock. It is used as facing stone, flooring, veneer and counter tops. The jetties in Ocean City and Assateague, Maryland, are made of gneiss. Gravestones are sometimes made from this rock. The intricate banded patterns give the rock an interesting appeal that makes it the perfect rock for smaller decorative items such as bookends, too.
Tags: used building, banded patterns, counter tops, decorative rock, decorative rock gardens, foliated rock, grade foliated