Feldspar: description and properties, who suits it. Feldspar group Potassium feldspar

Feldspar stone is one of the most common minerals on the planet. Many gems are a variety of spar. They are beautiful and are not inferior in uniqueness to expensive precious formations.

History of the discovery of feldspar

The history of the stone does not have an exact date for the beginning of the discovery and use of the field mineral by people. Descriptions of the mineral can be found in ancient sources from different eras. The name of mineralogy was given by a literal translation from German: a field mineral that splits into separate lamellar layers. But the term itself is not a discovery of the Germans. It was formed from the name of agricultural land in Sweden. They were strewn with pieces of spar. Therefore, the opinion of geologists who classify the mineral as a Swedish-German term is considered correct. Cleavage should initially sound like spatality, that is, strong cohesion, the strength of the fusion of plates. There is information about the discovery of the first spar jewelry. These are excavations on the territory of the ancient states of the East and Egypt.

Physical and chemical properties

The physical properties of any mineral group are the same, but the chemical content is different. The stone looks like a plate of heterogeneous composition fused into a single whole. Formed in the form of twin crystalline compounds.

Properties and features of feldspar stone:

• full degree of cleavage (perfect);
• the shine of glass and mother-of-pearl surfaces;
• the effect of the physical process of iridescence;
• The hardness of crystals and adhesions is average.

The composition of spar has been studied by mineralogists, all representatives are divided into classification subgroups:

• potassium Kalium;
• sodium Na - calcium Ca;
• potassium K – barium Ba.

The mineral is similar in origin to granite. It owes its creation to magma and acidic environmental structure.

1. The first type (potassium field minerals) is formed under hydrothermal conditions during the weathering of kaolinite. Stones of the group: microlins, sanidines, adularia.
2. A subgroup of sodium-calcium stones has the effect of twin rocks with a triclinic structure. Their common name is plagioclase. Representatives of the subgroup: albite, andesine, labradorite, oligoclase, bytownite, anorthite. The rarest and most valuable is solar albite.
3. The third subgroup of potassium-barium field minerals is the most valuable. It is found rarely, often as inclusions in another gem. The rocks are cream colored. One of the minerals of the species is celsian. This is a desirable find for collectors and lovers of special valuable pieces.

Deposits

The rock-forming mineral has several varieties. Deposits of each group are located on different soil layers and have different formation conditions. The earth's crust consists of 60% feldspar. Most land areas boast the presence of feldspar. Interestingly, the surface of the Moon is also rich in spars. Many meteorites are composed of feldspar.

Human use of spar is developing, so mining is widespread and active. On a production scale, feldspar is mined in the following countries:

• Kazakhstan;
• Poland;
• Japan;
• Madagascar;
• Germany;
• Switzerland;
• Ukraine.

Used for making jewelry, it is found in large quantities in other territories: Canadian, Indian and African republics and Brazil. Labradorite was developed in the mines of Canadian, Ukrainian deposits, China, Greenland and Indian lands. Orthoclase pleases archaeologists and miners of the Australian continent, America, Kyrgyzstan, the Italian and Mexican mountains. Adularia was developed in India, the island of Sri Lanka, the Republic of Tajikistan, and Switzerland. The mineral is mined high in the mountains, and the higher the mountainous country, the higher the quality of the gems.

Medicinal properties of feldspar

Feldspar has special healing value for humans. The range of medicinal uses is very wide. But the healing properties of each mineral included in the feldspar group are different. You should carefully study the capabilities of each gem so as not to harm your health.

The healing stone Labradorite provides the following therapeutic assistance:

• diseases of the musculoskeletal system;
• deviations of the genitourinary system;
• relieves insomnia;
• calms the psyche.

Healing properties of microlins:

1. Improving the functioning of vascular systems;
2. Normalizes the psyche;
3. Relieves stress;
4. Purifies the blood;
5. Takes you out of depression.

Albit treats kidneys and liver. Andesine is recognized as a powerful antidepressant mineral, comparable in effect to strong drugs.

Magical abilities and powers of feldspar

Feldspar gems are famous as magical stones. They are used by light and dark witchcraft forces, mediums and shamans.

Magical abilities of the stone:

1. Spiritual movement into the past and future;
2. Development of natural qualities and abilities;
3. Communication with spirits of other worlds;
4. Cognition and understanding of the Universe, connections of planets.

Magical powers of feldspar group stones:

1. Labrador helps older people. It imparts activity, positivity and optimism. The stone helps to maintain a good mood.
2. Microlins protect family relationships. Minerals help maintain home comfort and warmth in relationships.
3. Orthoclase can warn of upcoming changes in relation to loved ones. It changes color. Knowing about such abilities, a person begins to be more patient and attentive. This behavior helps to avoid scandals and quarrels.
4. Amazonite makes a person bold and confident. Gems change personal qualities. Rude people become reasonable, harsh people become wise.

Talismans and amulets

Adularia can be a talisman and protective talisman. Feldspar has magical abilities needed by creative people and specialties:

• develops imagination;
• gives clarity of thought;
• helps to construct speech clearly and logically.

An amulet made from adularia protects against the influence of the energy forces of black magic (vampires) on the human aura and protects against the evil eye.

Interesting video: Sunstone - feldspar

Feldspar colors

All varieties of stone in natural formation are colorless. The palette of colors is acquired by rocks with admixtures. Shades of orthoclase: pink, snow-white, red and yellow. Microline paints: bright red and orange. The group is called sun stones. They resemble a bright luminary, the surface seems to warm and radiate warmth. Amazonites are endowed with gray and green shades.

Labradorite shimmers with all the colors of the rainbow, the base of the mineral is often blue-black. It is sometimes called a cold rainbow, there are many colors, but they seem to have lost their brightness and saturation, while the shine remains. Iridescence adds an unusual attractiveness to the stone. Orthoclase has pastel colors; an admixture of gray can be discerned. The best samples are transparent in structure and colorless. There are stones with interesting internal contents of the rock: sparks and sparkles.

Adularia is comparable in color to the Moon. Its second name is moonstone. The color is mysterious, the luster of mother-of-pearl is deep. Jewelry stone attracts with the desire to look deep, to comprehend the hidden secret.

How to spot a fake

Jewelry stones are not all feldspars. For feldspar jewelry, crystals with iridescence and a transparent structure are chosen. In the photo of the stone, you can choose any product of the craftsmen. Necklaces are not only beautiful, but noble and discreet. The cost depends on the quality, complexity of the product and the metal of the frame. You can buy all kinds of jewelry. There is no point in counterfeiting them, since the rock aggregates are very common. But the most unique specimens, rare and beautiful, are almost impossible to buy. It's difficult to fake them.

Caring for products with spar

The main application is the ceramic industry. Feldspar is part of the material used to make porcelain. They are easy to care for and should be stored taking into account their fragility. It is not recommended for items to come into contact with each other or other products. Dust and dirt must be removed regularly. The best option is clean water without soap or special household products. It is necessary to dry the products; a layer of dust may again appear on the damp surface.

Feldspar and the zodiac circle

The number of minerals included in the feldspar group is so large that any of the zodiac constellations is compatible and can find an astrological assistant among the gems. The appearance of gems cannot be taken as a basis. Astrology has studied the compatibility and significance of minerals for humans.

Who is feldspar suitable for:

• Labrador – Virgo, Aries;
• Amazonite – Cancer, Taurus;
• Adularia – Pisces;
• Andesin - Lions;
• Albit - Leos.

The meaning of the stone is described in the sources of astrologers. You can find information about how feldspar affects humans.

According to the horoscope, the mineral does not suit other constellations of the Zodiac:

• Labrador – Cancer, Capricorn, Aquarius;
• Amazonite – Sagittarius;
• Adular - Virgo;
• Andesine - Gemini;
• Albit - Aquarius.

Feldspar - properties of the mineral, application and description of the stone

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Feldspar group

It’s safe to say that every person on the planet has held feldspar in their hands at least once in their life. This is a huge group of silicates, which occupies a significant share among all minerals. Translated from German, spath means “bar”. Apparently, this name came from the frequent finds of stones in the form of bars in the fields during cultivation of the land.

Feldspar is not a distinct mineral. It includes a whole series of nuggets, each of which has its own characteristics. Moreover, the crystal structure and chemical formula of all specimens are almost identical. Let's take a closer look at what types of stones are distinguished, in what form and where they can be found in nature, as well as in what areas of activity they are used.

Types of feldspar and their chemical composition

All silicates contain silicon dioxide as a base. There are three types of minerals of the feldspar group. Let's study each of them in more detail and understand their differences:

1. Potassium-barium feldspar;
2. Calcium spar or plagioclase.

Based on the name, it becomes clear that potassium feldspar necessarily contains potassium. Its structure also includes aluminum. The chemical formula is as follows: KAlSi3O8. This group consists of 4 minerals: orthoclase (moonstone), microcline, sanidine. Despite the identical chemical composition, they are all different from each other. This is due to the diverse ordering of particles in the crystal lattices of minerals.

Orthoclase got its name in 1823 due to the 90 degree angle between the cleavage planes. In Greek, orthos means “straight” and kalo means “I split.” Cleavage is the ability of a mineral to split along possible crystal faces. It is the parent rock for granites and syenites. Very often it contains sodium oxide, NaO2. Basically, the nugget is formed in the voids of acidic pegmatite rocks. So, it can be found in the Urals in Russia. The most beautiful and rare specimens of a delicate yellow color are found on the island of Madagascar.

Adularia is located in alpine-type quartz veins. The mineral received the name “moonstone” due to its unusual color and glow under direct rays of light, as a result of which it can be compared to a cosmic body. The cleavage angle is 30 degrees. Adularia is a rather rare stone, which is considered an analogue of orthoclase, with the only difference being that during the growth process the thermochemical reaction occurs at a lower temperature. The nugget is most commonly found in Sri Lanka, Australia, Brazil, India and Burma.

Microcline is also quite common throughout the world. Its cleavage angle is about 70 degrees. The stone often has albite inclusions. Similar formations in the earth's crust are found in places where igneous rocks and pegmatites are located. The color depends on additional inclusions of metals - it can be white, brown, pink, or less often green.

Sanidine was discovered in 1808, and first described only in 1959. It is characterized by impurities of iron, calcium, sodium and water. The structure of the stone has a good level of transparency and glass luster. Most often, sanidine is colorless or has a grayish-yellow tint.

In general, potassium spars are most often mined in the Scandinavian Peninsula, the United States and the island of Madagascar. The mineral is also widespread in Russia in the Ilmensky Nature Reserve.

Potassium-barium feldspar

It is rare to find silicates in nature in which potassium is replaced by barium. Such specimens include Celsian. Its chemical formula is as follows: BaAl2Si2O8. The barium oxide content is usually 34-42%. The crystals are well formed, have a short prismatic orthoclase appearance, sometimes rich in facets. The described sample has a weak density, so if handled improperly it will quickly crack. The color is predominantly white, with some colorless specimens occurring. Cream specimens represent a significant role for collectors.

Calcium spar (plagioclase)

Plagioclases are also classified into several individual minerals, each of which has different physical characteristics and a different appearance. They always contain the following chemical elements: Na2O, CaO, Al2O3, SiO2. However, the ratio of these substances in each nugget is different. The following minerals are distinguished:

• Albit is a white sodium silicate of igneous origin. Potassium, calcium, rubidium and cesium are found as impurities. The crystals are tabular, they are characterized by double nuggets - twins, the crystallization period for such specimens is slightly higher. Thus, in Figure 2 you can see twinned tabular albite crystals enclosed in a monoblock of green amazonite. The mineral was first described in 1815 by Swedish geologists. In addition to Sweden, it is found in Australia, Kenya, India, Japan, Russia and other countries.
• Oligoclase – it is also called sunstone or fish eye. Quite rare in nature. It is characterized by a glassy, ​​oily sheen. Transparent specimens are especially valued. The date of the official discovery of the mineral is considered to be 1824. This described mineral does not have a clear composition. All its specimens will differ from each other in the ratio of sodium, calcium, silicon oxides and additional impurities that provide different colors.
• Andesine - the nugget was first discovered and described in Colombia in 1841. It has a white or grayish color and a glassy sheen. Such a specimen rarely has a classical crystalline structure. It is usually presented in the form of granular aggregates; accordingly, it is characterized by a sinter type of formation.
• – divided into spectrolite, sunstone and black moonstone. All types of Labradorite are characterized by iridescence - an optical effect in the form of multi-colored radiance, which appears in bright light. After processing the stone, the shine and iridescent tints intensify - Figure 3. It was first discovered in Canada at the end of the 18th century.
• Bytownite is pure calcareous plagioclase, which has practically no additional elements in the crystal structure. The composition and physical properties of the stone are similar to labradorite. The main deposit is also located in Canada. This nugget is a translucent yellow crystal with a golden tint.
• Anorthite is a transparent and translucent silicate of white, gray or yellowish color and is a granular aggregate. Found in Karelia, the Urals and Ukraine.

Unlike potassium feldspar, all types of plagioclase are practically insoluble in acids. All of them are formed in igneous or metamorphic rocks.

The hardness of all types of feldspar varies from 5 to 6.5 on the Mohs table. When the minerals of this group are heated, the viscosity of the natural material increases. This property allows the use of nuggets in the construction industry.

Applications of feldspar

Along with the usual jewelry use for gems, minerals of the feldspar group are also used in other areas:

• Various ceramic products, widespread throughout the world, are created using clay - which often includes feldspar.
• During ore mining, spar is used as a flux or flux to facilitate the separation of metals from the rock.
• The glass industry also needs this silicate.
• Feldspar is used as a light abrasive, such as in the production of toothpaste.

The basis of our planet is the earth's crust. Without it, the existence of all living beings would be impossible. The main component of the earth's crust was feldspar, which is the rock-forming material for many minerals. The mineral acquired its name from the words “bar” and “arable land” due to the fact that it could often be found in plowed fields. The common people called the stone peeling off into small plates. Mineralogists consider it a rock.

A mineral may occur as a separate mineral. Or it may be part of other minerals. In nature, feldspar is born due to fiery magma and an acidic environment. In this way it is similar to granite - a rock consisting of spar, mica and quartz.

Spars, which are part of the field group, are valuable because they are extracted from the depths by open-pit mining. In those places where geologists have discovered a mineral, a pit is dug. Then, using special equipment, the solid gift of the Earth is extracted from it.

Mineralogists have found that the common name “feldspar” hides several stones, deposits of which are scattered throughout the world.

• The Democratic Republic of Madagascar supplies the world market with rare orthoclases of a beautiful soft yellow color.
• There are huge deposits of moonstone in Ukraine.
• The Socialist Republic of Sri Lanka gives heliotrope jewelry to the human community.
• Canada provides Amazonite.
• Greenland has developed mines where Labradorite is found.

Geologists mine a huge amount of high-quality spar in Russia.

• The Ilmensky Nature Reserve is famous for having proven reserves of potassium spar.
• The Republic of Karelia ranks first in pegmatite production. There are 72 deposits of stone that splits into plates.
• The Baikal region has Amazonite deposits.

Physicochemical properties and formula

Spars are silicates having a framework crystalline structure. All varieties of fossils have the same physical properties and look like monolithic plates of heterogeneous composition. But their chemical composition is different.

Mineralogists highlight the following physical properties of all spars:

• Perfect (complete) or good degree of cleavage.
• Hardness on the Mohs scale is approximately 6-6.5.
• Density is from 2.5 to 3.4, that is, the minerals have normal heaviness.
• Transparency.
• Light color.
• Glass shine.

Some specimens of spar have iridescence. That is, they have an optical effect that manifests itself in the form of a rainbow glow, especially noticeable in bright light. This property is enhanced if the stone, with its disintegrating layers, is polished.

There are several types of iridescence of the breed:

• Opalescence is considered to be a glow in bluish, greenish, pearly white and pale yellow tones. Or an iridescent shimmer of bluish-lilac or gray-blue tone, reminiscent of the iridescent color of the plumage of pigeons.
• Adventurescence - bright dotted highlights on the mineral in orange-red, bright yellow and crimson shades. This property is caused by reflections of light from the smallest hematitite plates scattered inside the spar.

The chemical formula of the stone looks like this - (Mx+M1-x2+) x(T2-x 3+,T 2+x4+)O8, where 0< х < 1. Шпат, входящие в группу полевых, обладают таким химическим свойством. Разные представители минерала по-разному реагируют с концентрированной соляной кислотой.

• Anorthite is easily dissolved by HCl, releasing a gelatinous precipitate - silica.
• Basic plagioclases dissolve with difficulty.

Some specimens are acid-resistant and do not disintegrate in acid.

Colors and varieties

The rock includes several varieties containing silicon dioxide and other chemical elements as a base.

Potassium spar contains potassium and aluminum and the finest intergrowths of coarse albite. This combination gives the minerals the effect of shining with moonlight. This group of fossils includes:

• Orthoclase is a universal crystal used by people in industry, jewelry, and as an ornamental material.
• Moonstone (also called adularia) is a rare spar with an amazing color and shimmer, reminiscent of the light of a night star. The unique appearance of the crystal is valued by jewelers. Jewelry with moonstone inlays is simply amazing.
• Microcline is a spar used in the ceramic industry for the manufacture of earthenware and porcelain products and technical ceramics. Decorative samples are used by craftsmen as jewelry and ornamental stones.
• Sanidine is an industrial raw material for glass production.

Potassium-barium spar is quite rare in nature. This group of underground gifts also includes celsian, a mineral that is valued by collectors.

Calcium spar (also called plagioclase) represented by several types of underground gifts:

• Albit is a mineral mined for the manufacture of ceramics, refractory and finishing materials.
• Oligoclase is a stone that is not often found in nature and is called sunstone or fish eye. Used in jewelry.
• Andesine is a gift from the Earth, used for the manufacture of fire-resistant, chemical-resistant, and heat-insulating products.
• Labradorite is a spar from which craftsmen carve solid columns, statues and pedestals.
• Bytovnit is a jewelry and ornamental material.
• Anorthite is an inexpensive stone for jewelry.

If the splitting stone does not contain additional impurities, then it is completely colorless. But if nature adds an additional chemical element to its formula, then spar acquires a white or reddish, pinkish, yellowish, greenish color.

A lot of different processes and reactions take place in the depths of the Earth. Several minerals, when combined together, can create a new rock.

For example, when spar, quartz, and mica combine, they form granite, known to many people. This gift from the Earth is very hard and strong. But time is merciless towards such items. Over the centuries, granite breaks down into individual components. The quartz then transforms into sand, and the spar and mica form clay.

Fisheye spar (video)

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Cutting features and price

On average, the price per ton of spar reaches 80 – 100 dollars. This figure may decrease or increase depending on the quality of the raw materials and the amount of impurities. Sanidine specimens are considered the most expensive. Due to its physico-chemical properties and traits, it is used to create bone china. Not all crystals are suitable for such use, since the creation of the substance requires raw materials that are completely free of dyes. The price per ton of stones is also high, which differ in:

• Rarities of color or shape;
• Cleanliness;
• Transparency;
• Color saturation;
• Degrees of perfection of the crystalline grid.

The cost of spar increases if the extracted mineral has the effect of iridescence or schillerization, that is, when the rays of the sun fall on the crystal, a rainbow or golden glow appears.

Scope of application

Due to its properties and a significant number of varieties, feldspar has found wide application in a variety of industrial sectors. Stone splitting into thin slabs use:

• Together with marble in the manufacture of glaze for decorating ceramics. Spar is flux, and marble is needed to lower the melting point.
• The crushed material is used as an abrasive substance for the production of whitening toothpastes.
• Spar is used to insulate cables and electrical appliances to create non-conductive materials.
• The rock is often used for cladding buildings, walls in subways, and also for creating monuments.
• Solid earth gift is useful when burying radioactive substances, since by reacting with dangerous compounds, it neutralizes them or slows down decomposition.

Magical and healing properties

The solid gift of the Earth has many magical properties:

• Spar will have a positive effect on a person’s existing abilities: he will be able to carry out familiar tasks without extra effort, concentrating his attention on more serious tasks that will help him move up the career ladder.
• Even our ancestors knew about the influence of material on interpersonal relationships. They gave each other pieces of this stone during conflicts, thanks to which a compromise quickly emerged. A similar ritual can be performed with the same piece of spar, passing it on to different people.

Use in jewelry (15 photos)

Astrologers' opinion

Spar is suitable for all people, however, it helps earth and water zodiac signs more than others.

• Taurus will be able to get rid of their fears by regularly rubbing the smooth surface of the spar. Despite further encounters with the phobia, the person will not experience any unpleasant sensations. His fear will finally disappear, and the person will be able to cope with a difficult situation without any problems.
• Virgo will be able to prove himself in new areas of activity. Self-realization will seem impossible in a profession to which a person has devoted most of his life. In order not to miss his chance, he will change his occupation and find his true calling.
• Capricorn with spar can become a real seducer. The hearts of representatives of the opposite sex will be easy prey, so he can easily find the ideal partner, choosing from many options.
• Cancer will be able to fulfill his dream, armed with spar. No matter what ideas he wants to implement, he will find the strength to do it. And new friends who appeared due to chance will become good helpers in this matter.
• If the solid gift of the Earth gets to Scorpio, then he will be able to deal with the biggest problems in a short time. A person can easily find a way out of the most difficult professional situations, thanks to which he can attract the attention of his superiors.
• Pisces, having acquired a crystal, will be able to find a common language with anyone. No matter with what intentions a person communicates with another, he will always get what he wants from the conversation.

Spar sunstone (video)

Artificial production and methods of distinguishing from counterfeiting

The most popular way to create an artificial crystal in chemistry is the synthesis of substances at high temperatures. The resulting stone consists of an alloy of glass with inorganic chemical elements.

There are several ways to help distinguish a fake from a natural stone:

• Spar takes a long time to heat up, since the transfer of energy between layers is a long process. The glass will become warm in your hand in 2-3 minutes.
• Despite the fact that in all physical and chemical properties a synthetic crystal replicates a natural one, it is lighter. Therefore, by comparing the masses of spar, you can easily determine which is real and which is fake.

Spar is an amazing stone that is quite common on our planet. However, its magical properties and influence on the signs of the Zodiac make it unique among other gifts from the Earth.

Feldspars are a large group of minerals that belong to the silicates. There are three types of these minerals according to their composition:

• sodium-calcium;
• potassium-barium;
• potassium feldspar.

Description

This mineral is widespread in nature. They have found application as a raw material for the production of rubidium and other substances, and are also used in the manufacture of glass and ceramic products. Most spars are representatives of solid solutions of the isomorphic series system (the formula for feldspar is Na - K - Ca).

Among these minerals there are many translucent and transparent, which are used as ornamental stones in jewelry. Highlight:

• andesine is a transparent or translucent variety of plagioclase, which has a color range of pink, yellowish, light green, orange-red and white;
• belomorite - a type of moonstone with light bluish reflections, in whose composition albite predominates;
• Labradorite (“Taus stone”, “peacock stone”) is a plagioclase moonstone that has a blue-black or dark blue color interspersed with the color scheme of a peacock feather;
• Bull's Eye is a brownish-purple variety of Labradorite that is tinged with red;
• spectrolite - a type of labradorite interspersed with colors throughout the spectrum;
• adularia is a moonstone that is a translucent or transparent type of potassium spar interspersed with a bluish-silver hue;
• Heliolite is a translucent or transparent orthoclase in red, orange and golden yellow hues that has a schillerizing effect. It consists in the presence of a golden-colored luster due to the content of inclusions of hematite flakes, as well as fine copper powder;
• Amazonite is a microcline in shades of vibrant bluish green and blue.

Feldspar stones have a hardness of 6-6.5 on the Mohs scale.

Feldspar: properties

All feldspars have similar physical properties. They all have cleavage in 2 directions (lateral pinacoids and parallel to the basal one, forming almost a straight or right angle), and general hardness. Two rare minerals - strontium stronalsite and barium banalsite - are of rhombic system.

Feldspar is the main rock-forming mineral of most rock igneous rocks (in addition to pyroxenites, ultramafic and alkaline rocks), in addition to various metamorphic rocks. The composition and type of mineral determine to a large extent the name of the rock. Feldspar makes up the bulk of pegmatites. It can occur in veined hydrothermal deposits. Stones are subject to weathering (exposure to groundwater seepage and atmospheric agents), leading to their further decomposition to form various clay minerals.

Glassy sanidine

Feldspar, such as glassy sanidine, can be found in the form of phenocrysts in rhyolites, as well as other extruded acid rocks. Often - in trachytes, in some potassium shallow intrusive alkaline rocks such as synnyrites, which received this name in honor of the Synnyr massif, located in the Northern Baikal region. The typical environment of this stone is granite, which can contain about 60% of this mineral.

Instead of orthoclase, granite often contains a potassium triclinic feldspar called microcline. Other intrusive rocks with a large proportion of orthoclase include syenite and granodiorite. The composition of feldspar, similar to intrusive acid rocks (trachyte, dacite and rhyolite), also includes orthoclase, often replaced by sanidine. In addition, orthoclase is found in migmatites, gneisses and other rocks of the highest degree of metamorphism, which were formed with the participation of granitization.

The mineral can appear in hydrothermal veins as a gangue mineral, especially at high temperatures. In addition, orthoclase can be found in arkoses (feldspathic sandstones). During its formation, sand grains accumulated so quickly that abrasion of feldspar with the formation of clay minerals did not occur.

Orthoclase

Monoclinic feldspar orthoclase is given its name by its cleavage at an absolutely right angle - potassium aluminosilicate. Although orthoclase is mainly found in the form of irregular grains in igneous rocks, it is capable of producing tabular crystals with one developed face strictly parallel to the lateral pinacoid. Twins are often encountered, especially of the Carlsbad type, in which there is a rotation around the twin axis with a fusion plane passing along the lateral pinacoid.

These stones are usually light in color, mostly white, sometimes pink or red (due to scattered hematite particles), and occasionally gray or yellowish. Orthoclase differs from other stones in its low density. A colorless, transparent or translucent variety of orthoclase in the form of crystals that resemble rhombohedrons is known as adularia; if it has a soft blue iridescence, it is also called moonstone.

Written granite

Feldspar, quartz, and mica intergrow. This mineral is called Jewish stone, or written granite, since the appearance of quartz ingrowths resembles Jewish writing. Intergrowths of sodium feldspar albite and microcline, forming lamellar ingrowths in the microcline, are called perthite.

Microcline

Microcline is a potassium triclinic feldspar with the same formula as orthoclase. In this case, sodium is able to partially replace potassium (although to a lesser extent than in orthoclase). Triclinic high-temperature alkali feldspar, which contains more sodium than potassium, is called anorthoclase. It is characteristic of some effusive, sodium-rich, less often alkaline, intrusive rocks.

Anorthoclase is very similar in physical properties, including the nature of twinning, to microcline. In addition to the Carlsbad and other simple twins that are characteristic of orthoclase, it can be polysynthetically twinned according to the albite law, while the lateral pinacoid is considered both an intergrowth plane and a twinning plane.

The intersection of these two series of strips at almost right angles produces a “lattice” effect when the microcline is observed in polarized light under a microscope. But only maximal microclines, which are characterized by a small degree of structural order, are considered lattice. The main color of microcline is white, less often pink or red, gray, and occasionally green.

Microcline

Microcline is a rock that is found in igneous rocks along with or instead of orthoclase. It is the predominant feldspar and at the same time the most common mineral of the series of granitic pegmatites, where its individual crystals reach several meters in diameter. For example, about 2000 tons of raw materials were produced from a crystal that was found in Karelia.

Plagioclases

The feldspar mineral also has another group - plagioclases (sodium-calcium triclinic feldspars), which form a constant series from sodium albite plagioclase to calcareous anorthite plagioclase.

Plagioclases are almost always twinned. Since this twinning is repeated many times in each sample (twins), the planes of this basal cleavage of plagioclases are covered on top with thin parallel streaks, which represent traces of contacts between twinned rocks and the emergence of twinned sutures to the surface.

Amazonite

Amazonite is a rock that is used as an ornamental stone. The mineral is mined in the USA, Russia (on the Kola Peninsula, the Urals and Transbaikalia), as well as in Madagascar. The potassium-sodium feldspars - microcline, orthoclase, anorthoclase, sanidine and albite - are generally called alkaline, forming one of the main groups in the spar family.

Grade

The price of feldspars directly depends on how rare their variety is. In addition, it is influenced by color, degree of transparency, the presence of schillerization and iridescence on the surface, as well as the place of their extraction. Thus, the price of one gram of green amazonite with a significant number of inclusions is $1-3, while samples of this stone of a dark turquoise pure tone are estimated at $10 or more per gram.

The most expensive of the feldspars is heliolite (sunstone), one bead costs $1.5, and a whole necklace costs $100.

Deposits

Feldspar deposits are found on all continents of our planet. The USA, Tanzania, Norway, Madagascar, and Russia can boast of heliolite deposits. In our country it is mined in Karelia and the Urals.

Adularia deposits are located in different countries of the East, including India, Sri Lanka, Tajikistan, in addition, in the USA, Switzerland, etc.

Amazonite is also mined in Ukraine, Central Asia, India, Brazil, Mongolia, Canada, etc.

Labradorite is mined in Canada, Ukraine, Egypt, Brazil, India, Norway, and Mongolia.

Magic properties

Feldspar is a mineral that has always attracted special attention for its unusualness, therefore, in the minds of people, such stones were endowed with all sorts of witchcraft qualities. The ability to develop mysticism and clairvoyance in a person was attributed to types of moonstone. Amazonite was considered a stone capable of strengthening family ties.

Medicinal properties

Lithotherapists use feldspars in the treatment of various diseases. Massage with amazonite balls easily relieves nervous tension and strengthens the heart. Labradorite is used to treat diseases of the joint-motor system, infertility, and inflammation of the prostate. But adularia is used in the treatment of mental disorders and epilepsy.

Cut

The main type of cutting of spar for jewelry purposes is considered to be the cabochon, which allows one to reveal all the beauty of the effects of shillerization, iridescence, cat's eye and asterism that are inherent in these minerals. At the same time, transparent mineral samples can be subjected to absolutely any cut.

Decorations

The hardness of minerals allows them to be used to create all types of jewelry and jewelry - necklaces, rings, bracelets, earrings, beads, brooches. For the setting of rocks that have iridescence or color in a cold range of bluish, blue, silver shades, a frame made of silver, white gold, medical alloy, cupronickel, etc. is used. Stones painted in a warm range are set in yellow or red gold.

Counterfeits and imitations of feldspars

Heliolite is counterfeited using glass containing copper flakes. At the same time, to imitate belomorite and adularia, frosted glass is used, which scatters light, although it does not have the bright characteristic reflections characteristic of natural stones.

Feldspars: who are they suitable for?

Jewelry with such lunar light stones as adularia and belomorite will look great on bright blondes, especially those belonging to the “summer” color type. Although they are also suitable for brunettes. Saturated amazonites, which are green in color, and orange-red heliolites will be combined with the appearance of brunettes, brown-haired women and girls who have mahogany or burgundy hair color. For girls with blond hair with a soft yellowish tint, as well as red-haired women, light green Amazonites and yellow-orange stones (spring and autumn color types) are suitable.

Astrologers advise wearing jewelry with adularia for Pisces and Cancer, and with amazonite for Aquarius, Gemini, and Libra. At the same time, there are no clear instructions about all other feldspars, therefore, all other signs can afford to wear them.

Diverse in effects and colors, feldspars today are increasingly attracting the attention of lovers of original jewelry with their interesting appearance, which makes it possible to add uniqueness to the image.

/ mineral Feldspar

Feldspars are a large group of widespread, in particular rock-forming minerals from the silicate class. Most feldspars are representatives of solid solutions of the ternary system of the isomorphic series K[AlSi3O8] - Na[AlSi3O8] - Ca[AlSi2O8], the end members of which are, respectively, orthoclase (Or), albite (Ab), anorthite (An).

There are two isomorphic series: albite (Ab) - orthoclase (Or) and albite (Ab) - anorthite (An).

Minerals of the first of them can contain no more than 10% An, and the second - no more than 10% Or. Only in sodium feldspars close to Ab does the solubility of Or and An increase. Members of the first row are called alkaline (K-Na feldspars), the second - plagioclases (Ca-Na feldspars). The continuity of the Ab-Or series appears only at high temperatures; at low temperatures, miscibility breaks with the formation of perthites. Along with sanidine, which is high-temperature, low-temperature potassium feldspars are distinguished - microcline and orthoclase.

Feldspars - most common rock-forming minerals, they make up about 50% of the mass of the Earth's crust.

General properties

Feldspars are silicates with a framework-type crystalline structure; these are openwork structures of silicon-oxygen tetrahedra, in which silicon is sometimes replaced by aluminum. They form rather uniform crystals of monoclinic or triclinic systems, in the form of a few combinations of orthorhombic prisms and pinacoids. Simple or especially polysynthetic twins are characteristic; The laws of twinning found in feldspars are divided into normal (perpendicular), for which the twinning axis is perpendicular to any possible face of the crystal located parallel to the plane of twinning, parallel, giving which the twinning axis is the edge of the crystal, and the plane of twinning is parallel to the twinning axis, and also more complex (combined) laws. In this case, the most frequently encountered are the albite (in plagioclase) and Carlsbad (in potassium field pshat) twinning laws.

All feldspars are easily etched by HF, and plagioclases are also destroyed by HCl.

Subgroups

Plagioclases
Plagioclases have the general formula (Ca, Na)(Al, Si) AlSi2O6:
Albite. (the extreme member of the isomorphic series, with the formula: NaAlSi2O6, contains 0-10% An.)
Oligoclase.
Andesine.
Labrador.
Bitovnit.
Anorthitis. (extreme member of the isomorphic series, with the formula: CaAlSi2O6, contains 90-100% An)

Origin

Plagioclases, mainly salic, are the main rock-forming minerals of igneous and many metamorphic rocks. In igneous rocks, plagioclase, rich in the An-molecule, first crystallizes, and then more acidic (rich in silica) is released. In these cases, zoned crystals may develop. Some igneous rocks consist almost entirely of plagioclases (anorthosites, plagioclasites, and others). Pegmatite veins often contain albite, formed from other plagioclases, and especially from sodium-containing potassium feldspars. Under hydrothermal conditions, plagioclases are altered by weathering into kaolinite minerals and sericite mica. At the same time, plagioclases rich in anorthite component are destroyed faster than acidic ones; albite is more stable during secondary processes.

Potassium feldspars

Potassium feldspars are often collectively simply referred to as "KPS":

• Orthoclase (KAlSi3O8)
• Sanidine (KAlSi3O8)
• Microcline (KAlSi3O8)

All three minerals correspond to the same chemical formula, differing from each other only in the degree of ordering of their crystal lattices.

Structural features and nomenclature

Approximate scheme of isomorphism in alkali feldspars

The microcline is of triclinic system (pseudomonoclinic), the angle between the cleavage planes differs from the straight line by 20°. Sanidine is monoclinic, with a completely disordered structure (K(AlSi)4O8), stable at temperatures above 500 ° C, and orthoclase, also strictly monoclinic, has a partially ordered structure K(A1,Si)Si2O8 and is stable at temperatures between 500 ° and 300 °C. Below this temperature, the stable form is microcline. Orthoclases almost always contain some amount of Na2O; intermediate members between orthoclase and albite are called anorthoclases. The orthoclase-albite series is usually stable at high temperatures; lowering the temperature leads to the precipitation of albite in orthoclase (perthite) or orthoclase in albite (antiperthite). The solid solution with sanidine is a monoclinic modification of Na[AlSi308] containing some potassium and is known as barbierite; another modification of the same composition, but triclinic, forms a solid solution with high-temperature albite. Varieties: adularia (named after an area in the Alps), low-temperature orthoclase with or without weakly developed facets (010), sometimes iridescent and used as a semi-precious stone (moonstone). Amazonite is a light green microcline. The crystallographic forms of pseudomonoclinic triclinic representatives are similar to those of orthoclase. Orthoclase is characterized by a right angle between the cleavage planes.

A staining method is used to distinguish plagioclases from potassium feldspars. To do this, the rock surface or mineral plate is etched with HF and then placed in a K-rhodizonate solution; — plagioclases, with the exception of albite, are painted brick-red.

Origin

Potassium feldspars are the main rock-forming minerals of acidic igneous rocks (granites, syenites, granodiorites, etc.), as well as some widespread metamorphic rocks (gneisses). The latter are dominated by low-temperature microcline, while igneous rocks of the plutonic type contain orthoclase, and volcanic rocks contain sanidine. Anorthoclase is a typical mineral of sodium-rich igneous rocks.

Orthoclase and microcline, together with quartz and muscovite, are the main minerals of pegmatites. If beryl is present in them, the microcline can be enriched in beryllium, which, like aluminum, can replace silicon atoms. Pegmatites are characterized by intergrowths of orthoclase (microcline) with quartz, known as “written granite” pegmatite and which are a product of crystallization of eutectic magmatic melt. Adularia is a typical feldspar in alpine-type hydrothermal veins.

Compared to plagioclases, K-feldspars are more resistant to destruction, but they can be replaced by albite, giving rise to “metasomatic perthite”. Under hydrothermal conditions and weathering, they change into minerals of the kaolinite group.

Deposits

Deposits of potassium feldspars are well known in Norway, Sweden, Madagascar, on the territory of the Ilmensky Nature Reserve and in many other pegmatite occurrences of the Southern Urals. Also in Maine, USA, and elsewhere.
Potassium-barium feldspars (Hyalophanes)
Potassium-barium feldspars (hyalophanes) are rare in nature. They are isomorphic mixtures of K[AlSi3O8] - Ba[Al2Si2O8].
Celsian (BaAl2Si2O8).
Hyalophane (K,Ba)(Al,Si)4O8
Quite a rare mineral. Individual cream-colored crystals have exclusively collection value.

Application

Feldspars are widely used in the ceramics industry as fillers, light abrasives (for example, in the production of toothpastes), and also as raw materials for the extraction of rubidium and some other impurity elements they contain. Due to its wide range of colors, feldspars are often used to make decorative decorations for home interiors, paintings and mosaics.

Some varieties of translucent and transparent plagioclase, which have an opalescent effect or silvery-bluish and golden iridescence, are used as ornamental stones in jewelry (moonstone, belomorite, labradorite).

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Properties of the Mineral

Color	colorless, white, gray, bluish, yellowish, pink, brownish, in principle, due to inclusions, can have any color
Stroke color	white
Origin of the name	from him. “feld” - field and Greek. “spate” - a plate, due to the ability to split into plates along the cleavage
Opening year	known since ancient times
Shine	glass pearl
Classes on taxonomy of the USSR	Silicates
IMA classes	Silicates
Fragility	Yes
Literature	Alekseev V.I., Sokolova N.G. Evolution of order and composition of alkali feldspars of the Northern granite massif (Chukotka). - Zap. RMO, 2007, part 136, issue 2, p. 62-74 Dolzhanskaya T.Yu. Use of typomorphic features of feldspars to identify the internal structure of the alkaline massif of the Cherry Mountains in the Urals. - App. and ecology aspects of minerals: abstract. report Godich. ses. All mineral. islands, Zvenigorod, March 19 – 21, 1990. Book 2. – M., 1991. – P. 61 – 63. Rus. Kupletsky V.I. Feldspars in the Kem region. - KEPS materials. L., 1924. Issue. 48. Stone building materials. pp. 29-46. Kurbatov S.S. Feldspars of the USSR and the possibility of using them in the ceramic industry. - Tr. State research ceramic in-ta. 1928. Issue. 2. P. 40.

Minerals Catalog