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Feldspar
Feldspar is a group of minerals that are the most abundant in the Earth's crust, making up about 60% of it. Feldspars are made up of aluminum, oxygen, and silicon atoms, and can contain varying amounts of potassium, sodium, calcium, and lithium.
Colors It Comes In -
White or buff to gray: This is the most common color for feldspar.
Pink or reddish: This is a common color for potassium feldspar also known as k-feldspar. Hematite inclusions can cause feldspar to be pinkish or reddish.
Green to blue green: This is the color of amazonite, a variety of microcline.
Yellowish: This is a color that plagioclase feldspar can range to.
Reddish brown: This is a color that plagioclase feldspar can range to.
Nearly black: This is a color that plagioclase feldspar can range to.
Fracture Pattern - blocky pieces with smooth sides
Shape - blocky or rectangular shape
Luster - glassy or vitreous
Texture -
Coarse:
Feldspar can have a coarse texture if it cools slowly.
Myrmekite:
A wormy texture that is characteristic of K-feldspar.
Microcline:
A wavy black-gray-white twinning that is characteristic of K-feldspar.
Perthite:
A texture that occurs when high temperature K-feldspar cools slowly and absorbs little blabs or crystals of sodic feldspar albite.
Zoning:
A distinctive effect that can occur when crystals vary in composition from core to rim.
Where It Can Be Found -
Igneous rocks:
Feldspar is a common mineral in igneous rocks, which form when magma cools.
Metamorphic rocks:
Feldspar can also be found in veins of other rocks as a metamorphic mineral.
Sedimentary rocks:
Feldspar is sometimes incorporated into sedimentary rocks, but it's not as resistant as other minerals.
Granite bodies:
Feldspar is mined from large granite bodies, called plutons by geologists.
Pegmatites:
Feldspar is mined from pegmatites, which are formed when the last fluid stages of a crystallizing granite concentrate into small pockets.
Sands:
Feldspar is mined from sands that are mostly made up of feldspar.
United States:
The top states for feldspar production in the United States are Virginia, South Dakota, California, Georgia, Idaho, Oklahoma, and North Carolina.
Hardness On The Mohs Scale - 6 Out Of 10