Skip to content

Venture into the Somber Hues of Iolite, a Gemstone Originating from Tamil Nadu

Iolite color variations studied in Gemmology Diploma project by graduate Nishka Vaz FGA

Exploring the Indigo Hues of Iolite Mining in Tamil Nadu
Exploring the Indigo Hues of Iolite Mining in Tamil Nadu

Venture into the Somber Hues of Iolite, a Gemstone Originating from Tamil Nadu

In the gemstone world, Iolites from Tamil Nadu, India, have been capturing the attention of collectors and enthusiasts alike. These unique stones, known for their vibrant colours and optical effects, have been found in various gem-bearing lithologies of the southern states.

Under magnification, the bloodshot iolites from Tamil Nadu display a colourful spangled effect, resembling a colourful glitter confetti. These stones can exhibit a wide range of shades, from pale, washed-out blues and violets to deep, inky blues that verge on black.

The search for iolites in Tamil Nadu has led gemologists to schists, granulites, and weathered gneisses, where they are found alongside minerals such as quartz, feldspar, sillimanite, biotite, phlogopite, haematite, diopside, actinolite, and more.

However, it is important to note that while Tamil Nadu is a prominent source of other minerals like garnet, ilmenite, and ruby, there is no clear evidence that it is a major source of iolite specifically.

Iolite is a magnesium aluminum silicate, chemically represented as MgAlSiO, and is known for its strong pleochroism—showing different colours (typically blue, violet, or yellowish hues) when viewed from different angles. This unique property makes it visually distinctive as a gemstone.

The pleochroic shade of blue in iolite resembles that of a sapphire and is called 'water sapphire'. Some bloodshot iolites from Tamil Nadu show a cat's-eye or star effect due to the reflection of light off haematite inclusions, a phenomenon known as chatoyancy and asterism.

Iolites from Arasanatham, Tamil Nadu, exhibit a rare and beautiful phenomenon known as bloodshot iolites, characterized by an abundance of hexagonal-shaped haematite platelet inclusions. In addition to their unique pleochroism, iolites from Tamil Nadu are capable of displaying a variety of optical effects, including spangled effects, chatoyancy, and asterism.

Sillimanite, calcite, diopside, amphibole group minerals, spessartine garnet, and apatite are some of the other minerals found as inclusions within iolites from Tamil Nadu.

The name 'iolite' is derived from the Greek word ion, which means violet. This gemstone's historical significance is evident in the Viking era, where iolite plates were used as a polarizing filter for navigation, earning it the name 'Viking Compass Stone'.

For those interested in learning more about iolites and other gemstones, Gem-A offers a Gemmology Foundation course and one-day workshops on a range of gemmological subjects. With the versatility and beauty of iolites from Tamil Nadu, these stones certainly are a sight to behold in any of their many forms.

  1. Gemmology Foundation course and one-day workshops on various gemmological subjects are offered by Gem-A for those fascinated by iolites and other gemstones.
  2. The name 'iolite' is rooted in the Greek word ion, signifying violet, reflecting its historical significance.
  3. Sillimanite, calcite, diopside, amphibole group minerals, spessartine garnet, and apatite are among the minerals found as inclusions within iolites from Tamil Nadu.
  4. In addition to their unique pleochroism, iolites from Tamil Nadu are capable of displaying a variety of optical effects, such as spangled effects, chatoyancy, and asterism.
  5. The pleochroic shade of blue in iolite resembles that of a sapphire and is called 'water sapphire'.
  6. Some bloodshot iolites from Tamil Nadu show a cat's-eye or star effect due to the reflection of light off haematite inclusions, a phenomenon known as chatoyancy and asterism.
  7. In the world of gemstones, iolites from Tamil Nadu, India, have been capturing the attention of collectors and enthusiasts due to their vibrant colours and optical effects.
  8. Iolite, a magnesium aluminum silicate (MgAlSiO), is known for its strong pleochroism, showing different colours (typically blue, violet, or yellowish hues) when viewed from different angles.
  9. The search for iolites in Tamil Nadu has led gemologists to schists, granulites, and weathered gneisses, where they are found alongside minerals such as quartz, feldspar, sillimanite, biotite, phlogopite, haematite, diopside, actinolite, and more.

Read also:

    Latest