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Last updated date: 23rd Apr 2024
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Sillimanite Meaning

The Sillimanite, also known as fibrolite is a stone that makes you feel delightful and fortunate to be alive. Sillimanite is highly exceptional and is found in two forms to include clear and glassy, or silky, and fibrous. In the fibrous form, the crystals are long slender prisms that look like fiber due to which is also known as fibrolite. The glassy stones are the ones that are used for making gemstones in jewellery because of their beautiful appearance. The sillimanite crystal is mostly available in the colour of green, but can also be in yellow, blue, white, or brown. The sillimanite hardness ranges from 6-7 making the stone difficult to cut. 

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Sillimanite  Mineral

Sillimanite, named after the American chemist Benjamin Silliman, is an aluminosilicate mineral with the chemical formula Al2SiO5 The term Sillimanite was first described in 1824 for an occurrence in Chester, US. A common form of Sillimanite is known as fibrolite. It is named fibrolite because the minerals occur like a bunch of fiber twisted together when observed in thin sections or by naked eyes. Both the fibrous and common forms of traditional Sillimanite are found in metamorphosed sedimentary rocks.  

Sillimanite Chemical Formula

The chemical formula of Sillimanite is Al2SiO5

Sillimanite Hardness

The Sillimanite’s hardness ranges from 6- 7 on the Mohs scale.

Sillimanite Crystal System

The Sillimanite’s crystal system is Orthorhombic

Sillimanite Chemical Composition

The Sillimanite’s chemical composition is Aluminium silicate

Sillimanite Color

The Sillimanite is usually colourless or white to grey, brown, yellow, yellow-green, grey-green, blue-green, blue, and colourless in thin sections.

Sillimanite Thin Section

The sillimanite thin section is colourless in-plane light, although the mats of fibrous sillimanite can be brownish/ tan. Under cross polars, it has second-order interference colour.

Sillimanite Cat’s Eye

Sillimanite cat’s eye is often referred to as fibrolite because the crystal occurs in a group, resembling fibers. It is found throughout the world in Srilanka, Myanmar, India, Italy, Germany, Brazil, and Czechoslovakia.

Sillimanite cat’s eye chemical formula is and the ratio of hardness on Mohs scale is 6-7.

Sillimanite Occurrence

Sillimanite, also known as Fibrolite is a brown, pale green, or white glassy silicate mineral that occurs in long, slender, needle-like crystals, generally found in fibrous aggregates. It is an index material indicating high temperature and variable pressure and is commonly found in metamorphosed clay-rich rocks (e.g, granulite and gneisses). The  Sillimanite mineral occurs in association with andalusite, kyanite, potassium feldspar, almandine, cordierite, biotite, and quartz in schist, gneiss, hornfels, and also often in pegmatites

Sillimanite Rock 

Natural Sillimanite rocks are cut into the required shapes and sizes and are generally used in glass industries. 

Sillimanite Applications

Sillimanite is considered an excellent raw material for the manufacturing of high quality alumni refractories or 55 - 60% alumina bricks. The use of Sillimanite on a large scale is not possible due to its high cost and fine grading.   

Sillimanite Crystal Benefits and Powers

Sillimanite crystal will help you to get back your excitement that tends to be lost when you work on something for long. It helps you to continue with your project and to feel the joy that comes with finishing it.

Emotional and Spiritual Influence

  • Sillimanite crystal will help you to uplift your sadness and depression. 

  • It also assists you to complete a task that seems impossible to complete.

The Physical Connection 

  • Sillimanite crystal is also thought to be good for stomach and digestive issues. 

  • It is also said that it helps the body assimilate after plates, screws, or other objects are added. 

  • It also treats the lungs, allergies, and sinus issues.

  •  It helps to slow down the ageing process.

Did You Know?

  • Sillimanite is a polymorph with two other minerals, Kyanite and Andalusite which implies that they have the same chemical composition but have a different crystal structure.

  • Sillimanite cat's eye is often referred to as fibrolite because its crystals occur in groups, resembling fibers.

  • Sillimanite formula is Al2SiO5.

  • Sillimanite is actually aluminium silicate, similar to prehnite.

  • Sillimanite is the only aluminium silicate that is known to occur with a cat's eye chatoyancy.

FAQs on Sillimanite

1. How to Identify Sillimanite?

The keys to identifying sillimanite are high relief, needle-like, fibrous or bladed habit, the characteristic cross square section with one diagonal cleavage.

2. What are the Different Sillimanite Colours?

Sillimanite is almost found in greyish to brownish colour in non-gemstone deposits. The rare colours which are often used as a gemstone include greenish-yellow, light bluish, bright to a purplish colour. The transparent sillimanite is usually greenish to yellow and in rare cases, colourless and light blue. Some Sillimanite exhibit different colours depending on the angle from which they are viewed.

3. What is Sillimanite Found?

Sillimanite is found at many points in France, Madagascar, and the eastern United States. A pale sapphire blue gem variety is found in the gravels of Srilanka.