Discover Everything About the Usambara Effect

The mesmerizing Usambara Effect in stunning Tourmaline (left) and Garnet (right), where the colors shift like magic under different lighting.

What Is The Meaning Of Usambara Effect?

The Usambara effect refers to the color-changing quality in gemstones, first observed in tourmalines from the Umba Valley in Tanzania. It is seen that the gemstones change color when they are exposed to different light settings and directions. This one-of-a-kind effect is typically named after the Usambara Mountains in Tanzania, where these marvelous gemstones were found. For Example - In the Umba area of Tanzania, some chrome tourmalines show a color change different from anything the miners have ever seen. Crystals of green chrome tourmaline from Tanzania might show a wine-red tone when viewed from certain directions.

The Usambara is not like many other color-changing effects, it is different from pleochroism, which involves different colors being exposed due to different angles in the same light. However, the Usambara effect does not change the color of a gemstone completely, the gemstones change the color in specific areas such as the straight middle line or corner line of the gemstone.

When Was The Usambara Effect First Discovered?

The Usambara effect is a unique color-changing phenomenon observed in a few specific gemstones. This distinctive effect was first discovered by a legendary Greek named Papas. Locals in the Umba area of Tanzania say that digging for chrome tourmaline started in the mid-1960s. Despite decades of digging, few people seem aware of the color change effect in these stones. The hype of the Usambara effect rose due to which the famous news journals started to write articles about it. The Usambara effect was first mentioned by A. Halvorsen and B.B. Jensen in a 1997 article published in The Journal of Gemmology.

In January 2000, French geologist Cedrick Simonet described the Usambara effect in tourmalines from Kenya in the same Journal. He later said that he had also seen this uncommon effect in garnets from Kenya making them exceptionally pleasant gemstones.

How Does The Usambara Effect Occur In Gemstones?

The Usambara effect can occur due to three reasons in gemstones:

1. The different shapes of the absorption spectrum,
2. the human eye's higher sensitivity to green compared to red, and
3. the increased absorption of green light relative to red light in thicker slices.

The above slide shows the transmission of light in the tourmaline reflecting a green color. When 2 slices are superimposed, the tourmaline shows orange to red tones.

Image Credit- Etsy

Please note:- The intensity of the color spectrum depends on the thickness of the gemstones. This happens because the gemstone absorbs different wavelengths of light at different depths. When light passes through a thicker part of the gemstone consisting of minerals like Chromium (Cr) and Vanadium (V), it travels a longer path, resulting in more light absorption and thus changing the gemstone’s appearance.

Which Gemstones Show The Usambara Effect?

This mesmerizing effect can be found in a variety of gemstones such as Tourmaline, Garnet, Alexandrite, Epidote, Purple Spinel, and Tanzanite (to name a few). All minerals showing the alexandrite effect may also have a component of the Usambara effect.

In tourmaline, the effect is particularly visible in varieties like chrome tourmaline, where the color changes from green to red. Garnets, specifically varieties like color-changing garnet, can also exhibit this effect, transitioning between shades of green and orange or red.

How Does The Usambara Effect Make a Gemstone Unique?

This color-changing feature, known as the Usambara effect, makes a gemstone more valuable because its stunning color shifts add a layer of intrigue and rarity that appeals to collectors and jewelry enthusiasts. It occurs in gemstones like tourmaline, garnet, Alexandrite , and tanzanite, making them particularly attractive and valuable to high-end collectors. Paraiba tourmalines, known for their vibrant blue and green hues due to copper content, have often fetched some of the highest prices in the market.

Conclusion

As seen, the Usambara effect is a fascinating and rare phenomenon that significantly enhances the allure and value of gemstones like tourmaline and garnet. This captivating color-changing property of the gemstones not only adds a visual appeal but also increases their market value. For collectors and jewelry enthusiasts looking to add these unique gemstones to their collection, it is crucial to purchase these gems from a reputable and authentic source.

At Gempundit, we pride ourselves on offering only the finest quality gemstones, meticulously sourced and certified for their authenticity. Our extensive collection includes gemstones exhibiting the stunning Usambara effect, ensuring you receive a genuine piece that meets the highest standards.