top of page

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

bottom of page