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Does Tanzanite Exhibit Pleochroism?

Published in Tanzanite Optical Property 2 mins read

Yes, Tanzanite exhibits very strong pleochroism, an captivating optical phenomenon where a single gemstone displays different colors when viewed from various angles. This unique property is a hallmark of Tanzanite, making it a highly sought-after gem.

Understanding Pleochroism in Gemstones

Pleochroism is an optical property displayed by certain anisotropic gemstones, meaning they have different optical properties in different directions. For gemologists, it describes the observation of different colors within the same material when viewed from varying angles. This phenomenon occurs because light entering the crystal is absorbed differently along different crystallographic axes.

  • Dichroism: Displays two distinct colors.
  • Trichroism: Displays three distinct colors. Tanzanite is a prime example of a trichroic gem.

Tanzanite's Remarkable Trichroism

Tanzanite is renowned for its vivid and strong trichroism, showcasing three distinct colors depending on the viewing direction. These colors typically include:

  • Blue: Often a vibrant, sapphire-like blue.
  • Violet: A rich, indigo-to-amethyst hue.
  • Burgundy/Reddish-Brown: A deeper, more subtle color, sometimes appearing brownish or yellowish in rough or untreated stones, which transforms into a richer burgundy after standard heat treatment.

This multi-faceted color display is what gives Tanzanite its distinctive allure and complexity.

Practical Implications for Gemstones

The strong pleochroism of Tanzanite has significant implications, especially in its cutting and appreciation:

  1. Cutting Orientation: Master gem cutters meticulously orient the rough Tanzanite crystal before cutting. The goal is to maximize the most desirable blue or violet hues when the stone is viewed face-up, as the final appearance is heavily dependent on how the crystal axes are aligned with the cut. Achieving the best color often means sacrificing some carat weight.
  2. Enhanced Visual Appeal: The ability to see different colors adds depth, dynamism, and intrigue to the gemstone. As you rotate a Tanzanite, you can observe a fascinating interplay of its signature blue, violet, and burgundy tones.
  3. Identification: Pleochroism serves as a crucial identifying characteristic for gemologists, helping to distinguish Tanzanite from other similar-colored gemstones.

Observing Tanzanite's Pleochroism

To fully appreciate Tanzanite's pleochroism, gently rotate the stone under various lighting conditions. You will notice the colors shifting and changing, revealing the full spectrum of its natural beauty. This optical property contributes significantly to Tanzanite's unique identity and its value in the world of fine jewelry.

For more in-depth information on pleochroism and other optical properties of gemstones, you can explore resources like the Gemological Institute of America (GIA).