Feldspar (noun)

1. A group of common rock-forming minerals that includes alumina, potassium, calcium, and sodium silicates.
2. A mineral that is a common constituent of granite, syenite, and other igneous rocks.

Origin:

From the german word feldspat, which literally means "field mineral.".

Examples:

1. Feldspar is an important ingredient in ceramics.
2. The feldspar in the rock sample was mostly plagioclase.
3. Feldspar is used as a flux in the production of glass.
4. The feldspar crystals in the granite were visible to the naked eye.
5. Feldspar is a common mineral in the earth's crust.