Did you know that the most abundant minerals in Earth’s crust are feldspars? That is a significant fact and so worth understanding more about them.
Feldspar refers to a group of silicate minerals that contain different ratios of the elements potassium, sodium, and calcium in combination with silicon and oxygen. Feldspar is a main ingredient in granite (orange crystals in the polished sample, right) but it is common in all three main rock types. Depending on their composition, feldspars range in colour from pinkish orange to white, grey, green, blue and black. They are all light weight, very hard, shiny and break in two prominent cleavage directions.
Some varieties of feldspar are semi-precious gems. One that is special to Canada is Labradorite, named for its occurrence in Labrador. It is bluish-black or greenish-black, and displays a beautiful iridescence (middle photo, right).
Large deposits of gabbro containing this beautiful mineral are commonly called (but not properly named) black granite. It is quarried for decorative facing stone on buildings and countertops (bottom photo, right).
Run of the mill feldspar is mined in many places all over the world, extracted from granites, pegmatites and certain sandstones. It is considered an industrial mineral that is used in the manufacture of glass, in ceramic glazes, paints, and a host of other familiar materials we use every day.
Industrial Mineral Association-North America