Resources of massive sillimanite of all grades are about 5.0%. The resources are located mainly in Tamil Nadu (27%), Odisha (20%), Uttar Pradesh (17%), Andhra Pradesh (14%), Kerala (11%) and Assam (7%).
Is sillimanite a gemstone?
Sillimanite (also known as Fibrolite) is found in various colours including green, yellow, brown, blue, white and even black. The gem is a complete Jekyll and Hyde; it can be discovered as a truly transparent gem, or completely opaque with a waxy lustre. …
How does sillimanite occur?
Sillimanite occurs as a constituent of high-temperature metamorphosed rocks containing clay. In contact metamorphosed rocks it may occur in silimanite-cordierite gneisses or sillimanite-biotite horfels. In silica poor rocks, it may be associated with corundum.
What rock is sillimanite found in?
Introduction: sillimanite is a metamorphic mineral found in high-grade rocks (upper amphibolite/lower granulite facies) most typically in aluminium-rich pelites. Sillimanite has two polymorphs, kyanite and andalusite, which develop under conditions of lower temperature and different pressure to sillimanite.
What is sillimanite used for?
Sillimanite minerals are mainly utilised in the production of mullite or high-alumina refractories. 95% of the world’s consumption of these minerals is used for this purpose in the manufacture of metals, glass, ceramics and cement.
What is sillimanite made up of?
Sillimanite is an aluminosilicate mineral with the chemical formula Al2SiO5. Sillimanite is named after the American chemist Benjamin Silliman (1779–1864). It was first described in 1824 for an occurrence in Chester, US.
How do you identify sillimanite?
Sillimanite is a metamorphic mineral found in high grade aluminous schists and gneisses. It is a polymorph of andalusite and kyanite, all having formula Al2SiO5. Keys to identification are high relief, needle-like, fibrous or bladed habit, characteristic square cross sections with one diagonal cleavage.
Which mineral is rich in India?
India has significant mineral resources of Coal (4th largest reserves in the world), Iron ore, Manganese ore (7th largest reserve in the world as in 2013), Mica, Bauxite (5th largest reserve in the world as in 2013), Chromite, Natural gas, Diamonds, Limestone, Titanium and Thorium (world’s largest along coast of Kerala …
Which state is the largest producer of sillimanite in India?
Orissa is the largest producer of sillimanite in India. Ganjam district is an important sillimanite producing district. Kerala is the second largest producing state.
What is sillimanite stone?
Sillimanite is a brittle stone, rating a 6-7 on the hardness scale. It is a very difficult stone to cut; therefore only skilled lapidaries should attempt to do so. It is a vitreous, and transparent to translucent stone.
What is sillimanite refractories?
Sillimanite refractories are characterized of high refractoriness, very low coefficient of thermal expansion, high refractoriness under load (RUL) and mechanical strength with great resistance to thermal shock (spalling resistance), abrasion and slag corrosion.
Does gneiss contain sillimanite?
Industrial Minerals and Rocks
Although sillimanite is known to occur in many high-grade gneisses and in some quartzites, no potential deposits have yet been found in Finland.
Is sillimanite high grade?
Sillimanite from a variety of high-grade metamorphic rocks contains from 0-13 to 1-82 weight per cent Fe2O3 and less than 0-1 weight per cent TiO2. The iron is trivalent and substitutes for Al only.
Who discovered sillimanite?
In Delaware, it is found in and around Hoopes Reservoir and Brandywine Springs. The Brandywine Springs boulders are remarkable for their size and purity. Sillimanite was discovered by scientist Benjamin Silliman (December 4, 1816-January 14, 1885) and named for him in 1850.
Are kyanite and sillimanite polymorphs?
Kyanite, andalusite, and sillimanite are naturally occurring anhydrous aluminum silicate minerals. Each has the same chemical formula, Al2SiO5, but differing crystal structures, making them mineral polymorphs.
What is the Colour of sillimanite?
Sillimanite occurs in three colored varieties: yellow, brown, and blue. The yellow color is characteristic of unaltered single crystals of sillimanite from high-grade metamorphic rocks and associated pegmatites.
How can you identify a sillimanite in a thin section?
- Relief: Moderate-High positive.
- Habit/Form: Sillimanite commonly occurs as slender prismatic crystals or as fine fibrous crystals called fibrolite. …
- Color: Usually is colorless; sometimes may be pale brown, pale yellow, brown, green, dark brown, blue.
- Pleochroism: None; sometimes weak to moderate.
Where is iron ore found in Assam?
Occurrence of banded-iron ore have been located in the Chanderdinga hills and Abhayapuri areas in Goalpara district and in the Aradanga- Rangchapara areas on the border of the Kamrup and Khasi and Jaintia hills districts. Quartz-magnetic rocks are stated to be available in the Hahim area within Kamrup district.
How common is pyrite?
It has a chemical composition of iron sulfide (FeS2) and is the most common sulfide mineral. It forms at high and low temperatures and occurs, usually in small quantities, in igneous, metamorphic, and sedimentary rocks worldwide. Pyrite is so common that many geologists would consider it to be a ubiquitous mineral.
Is sillimanite a good mineral to use for determining the grade of metamorphism?
Sillimanite is especially good for determining how close a rock is to melting because it forms first as andalusite or kyanite turns to sillimanite with increasing temperature (1st sillimanite isograd) and again when muscovite and quartz reacts to form sillimanite, K-feldspar, and water (2nd sillimanite isograd).