Feldspar Mineral Facts and Photos
What are Feldspars?
Feldspar is a general term for one of the most abundant group of minerals on Earth. Together the different varieties account for more than half of Earth’s crust.
Feldspars are important rock forming minerals that occur worldwide. As well as being a major component of most igneous rocks they're also found in sedimentary and metamorphic rocks. Feldspars have also been found on the moon and in meteorites.
The name "feldspar" (originally "felspar" but no longer used) comes from the German word "feld" meaning "field". This is because during the process of weathering and decomposition feldspars release nutrients which enrich the soil.
The variation in colour of different feldspar minerals depends on the impurities present.
Feldspars are widely used in industry mainly for the production of glass, ceramic and porcelain. Varieties such as labradorite, moonstone, sunstone and amazonite are used for decorative purposes, gemstones and for their metaphysical healing properties.
What is Sunstone-Moonstone?
A material that's being called "sunstone-moonstone" has recently appeared on the market. It's a trade name for a variety of feldspar correctly known as Peristerite.
"Sunstone-moonstone" is not a combination of sunstone and moonstone.
Trade names can often be misleading with regards to the chemical composition of a mineral. The name "Jasper" is widely used as a trade name but often for stones that contain no jasper at all.
Peristerite is a variety of the feldspar mineral albite. The stone's colour is often very similar to the material widely known as moonstone.
Peristerite can also have a similar appearance to labradorite.
White peristerite with a blue flash is often sold as "rainbow moonstone". Moonstone (and rainbow moonstone) are trade names for any variety of feldspar that exhibits a blue flash or silky/pearlescent lustre.
Peristerite is named after the Greek word "peristera" which means "dove". This comes from a perception that its colour resembles the feathers of a dove.
The blue flash is caused by the interference of light between thin layers of different feldspar minerals.
Flashes of blue, green, yellow and pink can often be seen. The optical effect in this mineral is known as adularescence or schiller.
The photo at the top of our article is feldspar. Courtesy of Stan Celestian.
The second photo is moonstone. Courtesy of James St. John.
Both images are clickable and redirect to the original photos.