What is Feldspar?

Feldspar is a blanket term for a very large group of minerals that are extremely abundant on Earth. Around 60% of the Earth's crust is made up of these minerals, in fact, and they have numerous uses for humans, ranging from scouring solutions to glassware. Chances are that most people are probably looking at something which contains feldspar right now, although they may not be aware of this, since these minerals are so ubiquitous in the industrial world. Globally, the major commercial sources are Italy, Turkey, China, and Thailand.

The distinguishing feature of minerals in the feldspar group is that they are comprised of silicates of aluminum blended with other metals like potassium, calcium, sodium, and sometimes barium. The composition of an individual piece determines its chemical properties and what color it will be, but it shares similarities with other feldspars, like a crystalline structure. Before feldspar can be used in an industrial process, it must be profiled to determine its chemical composition, as different types will of course behave differently.

Many feldspars are formed in magma, crystallizing out as the magma cools, making them igneous rock. It also appears in the form of veins in other rocks, formed through processes of pressure, classifying it as a metamorphic rock as well. Feldspar sometimes occurs in sedimentary rocks also. Regardless as to the process which led to their formation, feldspathic rocks contain blocky crystals.

In the Earth, one of feldspar's important roles is in clay formation; as the material weathers, it turns into clays. Humans use it in pottery and glassmaking, and it is also added to scouring powders and used as a filler in a wide range of products. Some are quite attractive, leading people to use them as semi-precious gemstones, as they can polish up quite nicely, and feldspar is also used to make decorative accents on buildings and monuments. It can also be used to date various materials, using a variety of techniques depending on the type of mineral involved.

Many natural history museums keep several excellent examples of various types of feldspar in an array of colors and sizes. Examining such a display can give people a good idea of the diversity of this mineral group, which appears in the ground we walk on, the glasses we drink from, and in a large array of other materials as well, ranging from tile grout to toilets.

Feldspar is a group of rock-forming minerals that make up about 41% of the Earth's continental crust by weight, according to the United States Geological Survey. It is commonly found in igneous, metamorphic, and sedimentary rocks, making it a significant component of both intrusive and extrusive rocks. Feldspar minerals are used in the manufacture of glass and ceramics.

There are two main types of feldspar, classified based on their chemical composition: plagioclase feldspar and alkali feldspar. Plagioclase feldspars contain calcium and sodium, while alkali feldspars contain potassium. These two groups encompass a variety of species such as orthoclase, microcline, and anorthite, each with unique properties and occurrences.

Feldspar minerals are known for their distinct cleavage, breaking along flat planes, and for their hardness, which ranks about 6 on the Mohs scale. They often display a glassy luster and can be found in a range of colors, including white, pink, or gray. Their crystal structure is typically blocky or tabular, and they may exhibit striations on some cleavage surfaces.

Feldspar is widely used in the industrial sector. It is a key ingredient in the manufacture of glass, where it acts as a flux to lower the melting temperature of quartz. In the ceramics industry, feldspar is used as a flux to improve the strength and durability of ceramic bodies. It's also used in paints, plastics, and rubber as a filler.

Feldspar is typically extracted through open-pit mining, where the mineral is drilled, blasted, and then transported to a processing facility. Here, it is crushed, ground, and separated from other minerals by flotation or magnetic methods. The processed feldspar is then milled to a fine powder for various industrial applications.

Yes, certain varieties of feldspar are used as gemstones. The most well-known gemstone forms of feldspar are moonstone, sunstone, and labradorite, which are prized for their optical phenomena such as adularescence and labradorescence. These gem-quality feldspars are cut and polished for use in jewelry, showcasing their unique reflective properties and colors.