Story of Feldspar

 

FELDSPAR

 

Type: Tectosilicate

Mohs hardness scale: 6–6.5

Color: white, gray, pink, brown, blue

 

ORIGIN AND PROVENANCE

Feldspar is a general term for a group of minerals characterized by the presence of aluminum oxide and silicon dioxide. They are the most important group of rock-forming minerals (up to 60%). Feldspars owe their name to the nutrients that are released into the soil during weathering and are essential for plant growth.

Feldspars are divided into two main groups:

* alkaline feldspars (sodium-potassium) – sanidine, orthoclase, microcline (amazonite), adularia (moonstone).

* Plagioclases (sodium-calcium) – albite-anorthite (labradorite), oligoclase (sunstone)

Several specific optical phenomena are associated with this group of minerals, such as labradorescence—a phenomenon in which colors change with a metallic luster, which can be observed in labradorites. Another optical phenomenon is adularescence—a milky or bluish sheen that occurs just beneath the mineral’s surface. Aventurescence, on the other hand, is a phenomenon caused by the reflection of light off the flakes of mineral inclusions, which form small, sparkling particles.

The most popular and most expensive type of feldspar used in jewelry is moonstone. The most popular moonstone is set in a necklace called the Iris Moonstone; it has a marquise cut, weighs nearly 36 carats, and comes from India (winner of the 2016 AGTA award). Florida has even declared it its state gemstone.

The most sought-after and best-known sunstones come from the state of Oregon in the U.S., where they have also become a state symbol. They were discovered in the 1980s and, thanks to copper inclusions, have a natural red or green color.

Also worth mentioning is amazonite, a potassium feldspar and a blue-green mineral with a white sheen. Some of the most beautiful turquoise-colored amazonites come from a mine in the Pike’s Peak area of Colorado in the U.S.

ORIGIN

Turkey, India, Italy, China, Iran, Thailand

USES

Feldspar is used in the manufacture of tableware and bathroom tiles. Feldspar is used as a flux in the production of glass and ceramics.