Orthoclase feldspar or moonstones has a delicate crystal structure, beauty, and long heritage making it perhaps the best-known gem-quality member of the feldspar group. Feldspar is the most abundant mineral in the Earth's crust, as well as some of the most diverse. You can pick up a rock anywhere in the world and you will likely find that it contains a mineral or two of the feldspar group. Moonstones or orthoclase feldspar have flash ghosts! As the stone rotates, the flicker of color and frightening glow moves around the gem, appearing and disappearing. Moonstones are orthoclase feldspar with a luster called Adularescence. Most elite moonstones have a blue luster or a rainbow of colors. The body color of these moonstones is colorless and semi-transparent. Tiny platelets that are too small to be seen create wobble, which reflects a bright color. Some moonstones are colorless and have a white shimmer. Sparkling blue and rainbow moonstones have become very popular lately. Once considered plentiful, they are now extremely rare due to increased demand and higher prices. However, it is still in the lower price category for small stones weighing less than a few carats. Large, brilliant blue, and rainbow-colored moonstones per carat will be priced in the moderate price category. Blue flash moonstones are found mainly in Sri Lanka; Rainbow moonstones are from India. More abundant and less lustrous are the translucent, pastel-colored moonstones from India; Many of these have eyes if the stones are cut to show the tangles. 
Available colors include peach, light green, yellow, and medium to dark grey. These moonstones are mystical in appearance and inexpensive. Today, moonstones are often carved into small works of art. Some of them are even sculpted with "Man on the Moon" faces. The cost of sculptures can fall into the moderate category if they are very unusual. Moonstone is a variety of the mineral orthoclase of the feldspar group. It consists of the minerals feldspar, orthoclase and albite. At first, the two metals overlap. Then, when the newly formed mineral cools, the similar orthoclase and albite separate into alternately stacked layers. When light falls between these thin, flat layers, it is scattered in many directions, producing a phenomenon called Adularescence. Adularescence is the light that appears to ripple through the gemstone, giving its surface a shimmering appearance. Perhaps the most attractive aspect of Adularescence is its appearance of movement. The misty light seemed to roll across the surface of the gem while changing the viewing angle. Other feldspar minerals can also show miscibility. One is labradorite feldspar found mainly in Labrador, Canada. Another labradorite, found in Madagascar, is multicolored on a light-colored body. It is known in commerce as rainbow moonstone, although it is actually a variety of labradorite rather than orthoclase. Canidine is another feldspar mineral that can include flat gemstones called moonstones. To be called moonstone, the actual identity of the mineral is not as important as the beauty of its fusion. 
feldspar crystal
Feldspars crystals are the most common minerals on Earth. In fact, if the entire composition of the earth's crust were considered as a single mineral, it would be calculated almost exactly the same as feldspar. Feldspars are complex aluminosilicate minerals containing K, Na, and Ca, with some rare Ba-rich species. The structures of these species are very similar. However, most feldspar crystallizes from the melting of igneous rocks. Structures at high temperatures differ from those at low temperatures. Furthermore, various compositions that may exist at higher temperatures may not be stable at lower temperatures. As feldspar cools, it can internally separate into separate mineral crystals, one type oriented within the other based on the symmetry of the host crystal. The specific type of interfacial growth, the composition of the minerals involved, and the size of the crystals involved depend on the original high-temperature composition and cooling history of the feldspar, which can be quite complex. It is easy to see why it can take mineralogist years to understand the intricacies of the feldspar group, not to mention the contribution of new data. Feldspar is an important and common raw material used in the production of ceramics and geopolymers. 
Feldspar is also often used as an anti-caking agent in non-dairy powdered creamer forms. Feldspar is an important component in the glass industry. The alkaline content of the feldspar acts as a flux, lowering the melting temperature of batch glass and lowering production costs. Followers of metaphysics believe that feldspar is a gemstone for creativity. Feldspar helps find unconventional and exciting ways to achieve goals by stimulating creative thinking. Feldspar increases your self-esteem, self-esteem, and self-awareness. Feldspar is believed to help align the chakras, subtle bodies, and meridians and is good for astral travel. Feldspar is associated with the astrological sign of Aquarius. Feldspar comprises approximately 60% of the Earth's crust, making feldspar the most common mineral. Feldspar contains aluminum silicate with potassium, sodium, calcium, and barium. The feldspar group consists mainly of 3 types of minerals: Microcline Feldspar: A type of mineral with the chemical structure of KAlSi2O8. Amazonite is the variety under this type of mineral. Orthoclase feldspar - mineral species with the chemical structure of KAlSi3O8. Moonstone (white, gray, peach, etc.) is the main variety of this type of mineral. Plagioclase feldspar - mineral species with chemical composition NaAlSi3O8 and CaAl2Si2O8). Sunstone, labradorite, and rainbow moonstone are the main types of this mineral. 
feldspar structure
The crystal structure of feldspar is based on the aluminum tetrahedron. Each tetrahedron consists of an aluminum or silicon ion surrounded by four oxygen ions. Each oxygen ion, in turn, is shared by neighboring tetrahedra to form a three-dimensional network. Tetrahedral aluminum silicate forms the backbone of feldspar crystals. The aluminum or silicon ion is surrounded by four oxygen ions in each tetrahedron. A three-dimensional lattice is formed when each oxygen ion is shared by an adjacent tetrahedron. You can see long chains of aluminosilicate tetrahedrons, which are often called crank chains due to their twisted shape. Each crank chain forms a three-dimensional network of four-atom fused rings by connecting to adjacent crank chains. The structure is open enough for cations (usually sodium, potassium, or calcium) to enter and balance the charge. Alkali feldspar has a configuration between the Or and Ab extremes. Plagioclase feldspar lies between Ab and An. There are no feldspars with an intermediate composition between the K (Or) and Ca (An) ends because these ions have different ionic radii and charges that would make the structure unstable. Some rare feldspars contain barium in their crystal structure. They are celsians (BaAl2Si2O8) and hyalophanes (a combination of K-feldspar and Celsius). They are also structurally similar to K-feldspar, and these minerals are very restricted in size and not as common as other feldspars. Plagioclase feldspar is the most common of the feldspar minerals because calcium is more common in the crust than potassium (3.6 and 2.8 percent of the crust, respectively). Plagioclase feldspar forms a continuous solid solution between the Ab and An ends at high temperature, but ion exchange must couple due to the charge difference between Na and Ca. The charge balance is maintained by replacing Al3+ with Si4+. The amount of potassium that can enter the lattice is limited by the large difference in ionic radius. 
feldspar crystal structure
What all feldspars have in common is the same arrangement of atoms, structural arrangement, basic chemical recipe, and silicate (silicon plus oxygen) recipe. Quartz is another structural silicate, consisting only of oxygen and silicon, but feldspar contains many other minerals that partially replace silicon. The basic recipe for feldspar is X (Al, Si) 4O8, where X represents Na, K, or Ca. The exact composition of many feldspar minerals depends on which elements balance the oxygen, which must fill two bonds (remember H2O?). Silicon forms four chemical bonds with oxygen; That is, it is quadrivalent. Aluminum consists of three bonds (trivalent), calcium forms two (divalent), and sodium and potassium form one (monovalent). So the identity of X depends on the number of bonds needed to get a total of 16. One Al leaves one bond to fill in Na or K. Two Al leaves one bond to fill in Ca. So, there are two different types of mixtures that can be used for feldspar, sodium-potassium series and sodium-calcium series. The first is alkali feldspar and the second is plagioclase feldspar. The two main types of feldspar are plagioclase feldspar and alkali feldspar. The only thing that generally differs in plagioclase is that its broken faces, the cleavage planes, almost always have tiny parallel lines crossing them. These cracks are signs of crystalline twinning. In fact, each plagioclase grain is usually a stack of thin crystals, each with its molecules arranged in opposite directions. Plagioclase has a range of colors from white to dark gray and is usually transparent. Alkali feldspar (also called potassium feldspar or K-feldspar) has a color range from white to brick red and is usually opaque. Many rocks contain feldspar, such as granite. Such cases are useful in learning to distinguish feldspar. The differences can be subtle and confusing. This is because the chemical formulas of feldspar mix perfectly with each other. 
orthoclase feldspar crystal structure
An important rock-forming mineral, orthoclase feldspar has a special crystal structure and it is the terminal potassium-bearing member of the potassium feldspar solid solution series. It is a main component of granite, its pink crystals give granite its typical color. Crystalline orthoclase can also be white, colorless, cream, pale yellow, or reddish brown. Orthoclase appears as short, well-formed prismatic crystals, which are often twinned. It can also occur in a bulky form. Moonstone is a variety of orthoclase that exhibits the Schiller effect. Pure orthoclase is rare, and there is usually some sodium in the structure. Specimens are abundant in igneous rocks rich in potassium or silica, in pegmatites and in gneiss. This mineral is important in pottery, to make the item itself and as a glaze. Orthoclase is a feldspar mineral with a chemical formula of KAlSi3O8. It is one of the most abundant rock-forming minerals in the continental crust. Orthoclase is widely known as the pinkish feldspar found in many granites and as a specified mineral with a hardness of "6" on the Mohs scale of hardness. Uses of orthoclase Orthoclase has many commercial uses. It is a raw material used in the production of glass, ceramic tiles, porcelain, tableware, bathroom accessories, and other types of ceramics. 
It is used as an abrasive in polishing powders and polishing compounds. It is also cut like a gemstone. The brilliant gem material known as moonstone is a growth between orthoclase and albite.
- Geological presence of orthoclase
Most orthoclase is formed during the crystallization of magma in intrusive igneous rocks such as granite, granodiorite, diorite, and syenite. Significant amounts of orthoclase are also found in extrusive igneous rocks such as rhyolite, dacite, and andesite. Large orthoclase crystals are found in igneous rocks known as pegmatites. Usually, only a few inches long, but the largest reported orthoclase crystal was over 30 feet long and weighed around 100 tons. It is found in pegmatites in the Urals in Russia. During physical weathering, orthoclase grains are incorporated into sediments and sedimentary rocks such as sandstone, conglomerate, and siltstone. Chemical weathering changes orthoclase in clay minerals such as kaolin in reactions similar to those described below. Orthoclase is also an important component of the metamorphic rocks known as gneiss and schist. These rocks often form during regional metamorphism when granite rocks are exposed to heat and pressure at converging plate boundaries involving continental crust.The orthoclase in these metamorphic rocks is inherited from their igneous stones.
- Orthoclase on the Moon and Mars
Orthoclase is also known in igneous rocks found on the Moon and Mars. Orthoclase is a major component of igneous rocks brought back from the Moon by astronauts. It was also discovered in igneous rocks on Mars during analysis by the NASA rover.
- Classification of feldspar minerals.
Feldspar Ore Classification: This triangular diagram shows how feldspar minerals are classified based on their chemical composition. The sequence of minerals along the left side of the triangle represents the alkali feldspar solid solution series. Orthoclase is found at the site of intense potassium content.
- Orthoclase as a feldspar mineral
Orthoclase is a member of the alkali feldspar series. Alkali feldspars include albite (NaAlSi3O8), anorthoclase ((Na, K)AlSi3O8), sanidine ((K,Na)AlSi3O8), orthoclase (KAlSi3O8), and microcline (KAlSi3O8). 
These feldspar minerals form a series of solid solutions between NaAlSi3O8 and KAlSi3O8. Minerals crystallize in this series of melts that normally contain sodium and potassium ions. At the time of crystallization, these ions can freely replace each other in the crystal structure of the mineral. Because of this, alkali feldspars are found in a range of chemical compositions between pure albite (NaAlSi3O8) and pure orthoclase (KAlSi3O8). A diagram is shown that summarizes the continuity of composition relationships. Because orthoclase is rich in potassium and is a final member of the alkali feldspar series, many geologists call it "K-spar", "K-feldspar" or potassium feldspar .