Garnet is the name used for a huge group of rock-producing minerals. These minerals share a familiar crystal composition and a generalized chemical structure of X3Y2 (SiO4)3. In that chemical composition, “X” can be Ca, Mg, Fe2+ or Mn2+, and “Y” can be Al, Fe3+, Mn3+, V3+ or Cr3+. Although garnet is often linked with the colour red. The red garnet gemstones can be encountered in almost any colour present and are well- recognized choices for jewellery of all types. That’s wonderful news if you’re in the market for this January garnet birthstone.
Occurrence of Garnet
These minerals are extensively found across the world in igneous, metamorphic, and sedimentary rocks. Most garnet stones are found near Earth’s surface when a sedimentary rock with greater aluminium content, such as shale, is put through heat and pressure intense enough to form schist or gneiss. Garnet is also found in the rocks of contact metamorphism, lava flows, deep-source volcanic outbreaks, subsurface magma chambers, and the soils and sediments formed when garnet-carrying rocks are eroded.
Chemical Properties of Garnet Stone
The commonly encountered minerals in the garnet group are inclusive of almandine, andradite, grossular, pyrope, spessartine, and uvarovite. They all possess a vitreous luster, a brittle tenacity, a transparent-to-translucent diaphaneity, and a shortage of cleavage. They can be found as solitary crystals, stream-tattered pebbles, granular aggregates, and gigantic occurrences. Their chemical structure, hardness, colours and specific gravity are listed below.
Garnet Mineral
|
Mineral |
Composition |
Hardness |
Colours |
Specific Gravity |
|
Almandine |
Fe3Al2(SiO4)3 |
7 – 7.5 |
red, brown |
4.20 |
|
Andradite |
Ca3Fe2(SiO4)3 |
6.5 – 7 |
Black, yellow, green |
3.90 |
|
Grossular |
Ca3Al2(SiO4)3 |
6.5 – 7.5 |
red, pink, green, yellow, clear |
3.57 |
|
Pyrope |
Mg3Al2(SiO4)3 |
7 – 7.5 |
red to purple |
3.56 |
|
Spessartine |
Mn3Al2(SiO4)3 |
6.5 – 7.5 |
orange to red to brown |
4.18 |
|
U20733431 |
Ca3Cr2(SiO4)3 |
6.5 – 7 |
green |
3.85 |
Physical Properties of Garnet
|
Chemical Classification |
Silicate |
|
Chemical formula |
X3Y2(SiO4)3 |
|
Luster |
Vitreous |
|
Diaphaneity |
Transparent to translucent |
|
colour |
Essentially red, but can be orange, yellow, green, purple, brown or black. Blue garnets are there but extremely rare |
|
Identifying characteristics
|
Hardness Specific Gravity Isometric crystal formation Lack of cleavage |
|
Streak |
colourless |
|
Cleavage |
None |
|
Mohs Hardness |
6.5 to 7.5 |
|
Specific Gravity |
3.5 to 4.3 |
Uses of Garnet Mineral
Following are the uses of garnet stone:-
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abrasive blasting granules
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abrasive grits and powders
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Filtration granules
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Waterjet cutting granules
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Gemstones (such as garnet birthstone, garnet earrings).
Garnets Gemstones
Garnet as gemstones has been in use for over 5000 years. It has been encountered in the jewellery of different Egyptian burials and was the most prominent gemstone of Ancient Rome. It is an alluring gem which is generally sold without treatment or enhancement of any kind. It is also durable and common that it can be used in jewellery as garnet earrings, garnet rings etc at a relatively low cost.
Even until now, garnet continues to be a popular gemstone of contemporary times. It caters to as a birthstone for the month of January and is a long-established gem given on a second anniversary.
Garnet Varieties
1. Almandine
A frequently found gemstone in the garnet family, almandines come in a huge array of colours. The mix of almandine-pyrope is the dark red variety customarily linked with garnets.
2. Andradite
One of the rarest garnets, these have the highest dispersion of all garnets, even greater fire than diamond. Demantoids, a variant of andradite, are particularly treasured.
3. Grossular
In contrast to other garnets in the family, grossulars are rarely red or even dark. However, they do form in every colour, even colourless, only other than blue. Their vibrant colours make them remarkable jewellery stones. Tsavorites contain an emerald-like green colour and can be a directive of high prices.
4. Hydrogrossular
Never transparent, these are often blueish green in colour. However, Hydrogrossular garnets are sometimes also found in white, pink, and grey.
5. Pyrope
Chrome pyropes display a red that can rival rubies. However, pyrope garnet stones have a very dark tone.
Fun Facts
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The garnet family is one of the most in the gemological world.
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Although garnet is frequently linked with the colour red, these gemstones can be found in almost any colour and are preferred choices for jewellery of all types.
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Garnet is believed to be a red gemstone; however, it occurs in a variety of colours.
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Gem-quality garnets precipitate in every colour – with red being the most common and blue garnets being particularly rare.