What is Garnet ?

Garnet is a large group of stone-forming minerals. These minerals have a common crystal structure and a general chemical composition in the form of X3Y2 (SiO4) 3.

Although garnet is commonly found in red, these gemstones can be found in almost any color, and these colors are usually popular choices for jewelry. The garnet family is one of the most complex among the gemstone family. It is not a single species but consists of several species and subspecies.

These minerals are often found in metamorphic, igneous and sedimentary rocks. Most garnets found near the earth's surface form when sedimentary rocks with high aluminum content, such as shale, are heated and pressed enough to produce schist or gneiss. Garnet can also be found in contact metamorphic rocks, subsurface magmatic chambers, lava flows, deep-source volcanic eruptions, and soils and sediments due to erosion and erosion of garnet-bearing rocks.

Most people know garnet as a red gemstone. However, they are often surprised to find that garnet is available in many other colors and has many uses. In the United States, the major industrial applications of garnet are waterjet cutting (35%), abrasive blasting media (30%), water filtration granules (20%), and abrasive powders (10%).

Garnet History

The word "garnet" comes from the medieval Latin granatus, meaning "pomegranate", due to the red color of garnet. Garnets have been used as precious and abrasive stones since the Bronze Age, and ancient Egyptian pharaohs wore necklaces full of red garnets. Sign rings in ancient Rome contained garnet, which was used to seal wax that provided important documents. The medieval clergy and nobility held red garnets.

Garnet is actually a group of several minerals. Five of these are pyrope, almandine, spessartine, grossular and andradite, which are very important gemstones. pyrope, almandine is available in purple to red. spessartine is found in exciting orange and yellow colors, while andradite is more common in yellow to green colors (a variety of demantoid gemstones). Grossular may have the widest range, from colorless to yellow to reddish-orange and orange-red, as well as a vibrant green called tsavorite.

In The Smithsonian's antique pyrope hair comb is one of the most famous pieces of garnet jewelry (pyrōpos from Greek means "fiery eye"). A large garnet of cut flowers sits in the crown. Pyrope garnets adorning the tiara-like jewel were mined from historic mines in Bohemia (part of the Czech Republic), and these red beauties were very popular when the piece became fashionable.

According to Indian astrology, garnet helps to eliminate negative emotions (depression, guilt) and builds more self-confidence and mental clarity in humans to improve creative thinking and peace of mind. In ancient times and the Middle Ages, gemstones such as garnet were thought to be a remedy for inflammatory and heart disease.

Garnet Properties

Minerals in the garnet group usually include almandine, pyrope, spessartine, andradite, grossular, and uvarovite. All granites have glass gloss, transparent-to-translucent diaphaneity, brittle strength and no gaps. They can be found in the form of single crystals, worn-out pebbles and granular aggregates. Their chemical composition, specific gravity, hardness and color vary.

There are different types of garnet and each has a different chemical composition. There are also solid solutions between most garnet minerals. This wide variety affects many of their physical properties. For example, calcium garnets generally have lower specific gravity, lower hardness, and are also green in color. In contrast, iron and manganese garnets have higher specific gravity, higher hardness, and are typically red in color.

How Does Garnet Form ?

·        Garnet in Metamorphic Rocks

Most garnets form at the boundaries of the convergent plate, in which the shale operates by regional metamorphism. The heat and pressure of metamorphism breaks the chemical bonds and causes the minerals to regenerate into structures that are constant in the new pressure and temperature environment. Aluminum garnet, almandine, is formed in this environment.

With the metamorphism of these rocks, garnets are formed into fine grains and gradually grow as the metamorphism progresses. As they grow, they move, replace, and incorporate surrounding rock materials. Simultaneously with the growth of a number of mineral grains, the host rock was included. This is why many of the garnets formed by regional metamorphosis are so involved.

·        Garnet mica schist in thin section

Garnet has grown by replacing, displacing and containing the mineral grains of the surrounding rock. It is very difficult to find clean and quality garnets without any conflict. It is difficult to understand how garnet can turn into good crystals in difficult conditions.

Calcium garnets are usually formed when alloy limestone is converted to marble by contact deformation along the edges of igneous intrusions. These are andradite, grossular, and uvarovite, which are slightly softer, and green garnets are less specific gravity. Two calcium garnets are very popular in the gem trade. They are tsavorite (light green grossular) and demantoid (green-gold andradite).

Garnet is a mineral in skarn. Skarns are metamorphic rocks and have been chemically and mineralogically altered by metasomatism. In the process of metasomatism, hot and chemically active liquids pass through the rocks, causing them to recrystallize and change composition. Skarns are often rich in garnet, pyroxene minerals, carbonate minerals and quartz.

·        Garnet in Igneous Rocks

Garnet is usually present as a by-product mineral in igneous rocks such as granite. Many people are familiar with Almandine garnet because it is commonly seen as dark red crystals in igneous rocks used as granite countertops. Espartine is an orange garnet found as a crystal in granite pegmatites. Pyrope is a red garnet found in peridotite fragments that is separated from the mantle during deep volcanic eruptions and brought to the surface. Garnet is also found in basaltic lava flows.

·        Garnet in Sedimentary Rocks and Sediments

Mineral garnets are often durable. They are usually found in soils and sediments composed of worn garnet rocks. Alluvial garnets are often the target of extraction operations because they are easy to extract and easily removed from sediment / soil by mechanical processing.

Garnet Color

Although garnets cannot be identified by color alone due to the wide range of overlapping colors, there is information on garnet colors.

·        Uvarovite: dark green.

·        Pyrope: purplish red, pinkish red, orangey red, crimson, dark red.

·        Almandine: deep red, brownish red, brownish black, violet red.

·        Malaia: various shades of orange, red-orange, peach, and pink.

·        Rhodolite: usually has a distinctive purplish color.

·        Grossular: colorless, white, gray, yellow, yellowish green, green (various shades: pale apple green, medium apple green, emerald green, dark green), brown, pink, reddish, black.

·        Spessartine: red, reddish orange, orange, yellow-brown, reddish brown, blackish brown.

·        Andradite: yellow-green, green, greenish brown, orangey yellow, brown, grayish black, black.

Garnet Sizes

Garnet crystals are often small, from microscopic to about 6 inches in the case of grossular. In general, many sediments are small grains of crystals on or on the host rock. Garnets in stone, with weak external shapes, can be much larger, such as almandine from Gore Mountain, New York, which reaches 60 cm in diameter. There are several spessartites in Brazil that weigh a few pounds and have good clarity and color. However, these cases are very rare. The diameter of a garnet crystal is about half an inch to an inch.

Garnet Care

To care for garnets, it is best to clean them with warm water, detergent and a soft brush. Although garnets are relatively hard, they can be a little sensitive to heat, so extreme heat should be avoided. For more information, consult the Gemstone Care Guide and the Gemstone Jewelry Cleaning Guide.

Garnet in the industry

·        Garnet Abrasives

Abrasives were the first industrial use of garnet. Garnet is a relatively hard mineral with hardness between 6.5 and 7.5 on the Mohs scale but is variable. This makes it an effective abrasive in many types of production. When crushed, it often turns into angular pieces that provide sharp edges for cutting and sanding. Small granules of uniform size attach to the paper to form a red sandpaper, which is widely used in carpentry shops. Sold as abrasive granules and powder. In the United States, New York and Idaho are important sources of industrial garnet for abrasives.

·        Waterjet Cutting

Most industrial use of garnet in the United States is in waterjet cutting. The machine, known as waterjet cutting, is a high-pressure jet with abrasive granules that, when directed at a piece of metal, ceramic or stone, can create a cutting action that generates little dust. And cuts at low temperatures. Waterjet cutting is also used in manufacturing and mining.

·        Abrasive Blasting

Garnet granules are used in abrasive blasting, which is called "sand blasting". In these processes, a tool presses abrasive granules with a surface using a highly pressurized liquid, often air or water, as a propellant. Abrasive blasting is usually done to smooth, clean or remove oxidation products from metals, bricks, stones and other materials and is much faster than sanding by hand or sanding machine. In general, this can clean small and complex surfaces that other cleaning methods lose. Abrasives of varying hardness are often used to clean the surface with greater difficulty, without damaging the surface.

·        Filtration

Garnet granules are commonly used as filter media. Small garnet particles are used to fill a container through which liquid flows. Garnet pore spaces are small enough to allow liquid to pass through, but they are too small to allow some contaminants to pass through the filter. Garnet is suitable for this application because it is relatively ineffective and has a relatively high specific gravity. Garnet granules, about 0.3 mm in size, are used to filter contaminants to a few microns in diameter. Due to its specific gravity and high hardness, carnet reduces the expansion of the substrate and the wear of the particles during the re-washing of the liquid.

Garnets as Gemstones

Garnet has been known as a gemstone for about 5,000 years. This stone has been seen in the jewelry of many Egyptian burials and has been one of the most popular gemstones of ancient Rome. This is a beautiful piece of jewelry that is often sold without any treatment. It is also durable and common and can be used in jewelry at an inexpensive cost.

Garnet is a popular gemstone in the global market today. Garnet also serves as a January birthstone and is a traditional gem given on the second anniversary. When people hear the name "garnet", they think of a red gemstone because they do not know that garnet is available in a variety of colors. However, there are gem quality garnets in every color, from red, which is the most common, to blue garnets, which are rarely found.

Red almandine is actually red garnet that is often found in jewelry, so it is very abundant and inexpensive. Pyrope and spessartine are also red garnets and are commonly found in jewelry. In recent decades, green demantoid garnet has become very popular. Its dispersion is equal to 0.057, which gives it a "fire" that is higher than diamonds. Green tsavorite has a bright and rich color that resembles emerald. It is usually used as an alternative to emerald. Both of these green garnets are very popular, but they are much more expensive than almandine.

Garnet Varieties

Species

·        Almandine: The best-selling gemstone in the garnet family is available in a wide range of colors. The almandine-pyrope mixture is dark red and is popularly associated with garnet.

·        Uvarovite: This type of garnet is the rarest stone in the garnet family and has a dark and rich green color that competes with emerald. Coated items are always small and very rare.

·        Grossular: Unlike other garnets, these gemstones are rarely found in red or dark colors. They are present in any color, even colorless, except blue. Light to medium tones and vibrant colors make them excellent gemstones.

·        Andradite: It is one of the rarest garnets. These garnets have the highest dispersion rate of all garnets and also have more fire than diamonds. Green demento is very precious.

·        Hydrogrossular: These garnets are not transparent at all. They are usually bluish green, but are sometimes seen in pink, white, and gray. Even the Hydrogrossular classification as a garnet species is debatable to some extent.

·        Pyrope: Chrome pyrope is a type of red garnet that usually competes with ruby. However, they have a dark tone.

·        Spessartite: This type of garnet is also known as espartine. This rare garnet is available in a variety of orange colors. Mandarin garnet is often sought.

·        Non-gem garnet species: Non-gem garnet species include goldmanite, henritermierite, kimzeyite, majorite, schorlomite, and yamatoite.

Blends

·        Rhodolite: This garnet is a combination of pyrope and almandine with a distinctive purple color.

·        Malaia: The term was originally used to describe a combination of pyrope and spessartite garnets.

·        Color change garnets: Garnets that turn blue in artificial light. In the late 1990s, blue garnets seen under incandescent lights with red-purple flashes were discovered in Madagascar. These discolored stones are pyrope-spessartite blend. Some Idaho garnets have a strong color change from red to purple. These are an almandine-pyrope compound.

·        Almandine-pyrope

·        Almandine-spessartite

·        Andradite-grossular

·        Pyrope-spessartite

Garnet identification

Nowadays, garnet identification is complicated. In the last fifty years, several new compounds have been discovered in East Africa. There is no reason to believe that all possible compositions have been discovered because we do not know what the future holds for lithologists.

Garnets have common properties at the molecular level despite significant changes.There are several changes in chemistry. However, they all retain the same basic structure. Garnets crystallize in an isometric system. The most common of these is the trapezoid, but strangely enough, they rarely form into cubes or octagons, which is the most common form of other isometric minerals. Garnets can be massive, granular, and have pebbles.

For many years, rhodolite has been described as a part of almandine and two parts of pyrope in gemology education. However, describing garnets is not that simple. Rhodolite gems, and other garnets, have some other species in their composition. It may be present in very small quantities, but garnet never contains only two raw materials. Also, a series of solid states such as an almandine-pyrope compound does not mean a combination of two types of molecules, Fe3Al2Si3O12 and Mg3Al2Si3O12. Instead, this means that the structure contains Fe and Mg.

Garnet is practically not found in pure form in nature. The purest gem-quality pyrope ever discovered contains about 83% pyrope, 15% almandine and about 2% garnet. The same is true of Almandin and Gorsular. 80% related to the purest items that exist. However, andradite and spessartite garnets have been found to be up to 95% pure. Also colorless and non-gemstone-sized garnets of 97% pure pyrope were found.

Garnet as a gift

Garnet also acts as a January birthstone and is a traditional gem given on the second anniversary.Born in January, they are very lucky to have beautiful and very diverse garnet as their cornerstone. Garnets are often red, but come in a variety of beautiful colors, including orange, yellow, purple, and vibrant green. There are even garnets that change color from blue to purple in different lights. Some believe that the true value of garnet birthstone is its power to provide health, wealth and happiness to the wearer.