Kunzite- an Elf with “Very Peri” Color

Lab updates

February 2023

Author: GUILD


Kunzite is one of the most famous varieties of spodumene, and it is known for light pink to violetish purple. Kunzite was named after pioneering gemologist George Frederick Kunz, who was the first one to identify a pink stone from California as a variety of spodumene in 1902. Kunzite was found in Brazil, Afghanistan, Madagascar, and Nigeria (Mauthner, 2011).


Recently, some kunzites were sent to Guild Gem laboratories for identification. These samples displayed remarkable pink, violet, and purple color (figure 1). They show obvious violet and light pink pleochroism (figure 2) and a refractive index of 1.6601.676. Relatively high birefringence makes them show double images (figure 3A). Both standard gemological and infrared spectroscopy (figure 4) indicate that all of these samples were kunzite.


Figure 1. The samples display charming light pink and violet. Photos by Huixin Zhao.




Figure 2. The purplish pink sample (top) displays violet and light pink dichroism under the dichroscope (bottom). Photos by Huixin Zhao.


Most of the samples display vivid and vital brilliance due to proper proportions and excellent cutting. Since the kunzite was formed in pegmatite deposit, it is often large and almost clean inside. In some samples, many long needles (figure 3B) and several transparent crystals (figure 3C, D), identified by Raman as muscovite and quartz (figure 5-6) respectively, were observed. In the ore vein of pegmatite formed many minerals such as tourmaline, muscovite, beryl, lepidolite, and quartz (Mauthner, 2011). Therefore, it is common to observe these minerals in the kunzite crystal.


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Figure 3. Internal features of kunzite. A: Distinct double images; field of view 12.30 mm. B: Long needles; field of view 5.83 mm. C: An irregular transparent muscovite with its image; field of view 2.06 mm. D: An irregular transparent flake quartz; field of view 2.28 mm. Photomicrographs by Huixin Zhao. Darkfield illumination.


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Figure 4. The infrared spectrum of kunzite.


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Figure 5. The Raman spectrum of muscovite (black line) observed in kunzite. Peaks in the inclusion spectra that are marked with an asterisk are from the host kunzite.


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Figure 6. The Raman spectrum of quartz (black line) observed in kunzite. Peaks in the inclusion spectra that are marked with an asterisk are from the host kunzite.


Ultraviolet-visible absorption spectrum (figure 7) shows a distinct Mn3+-related band centered at 535 nm (Laurs et al., 2008). The intensity of peaks is related to the color depth, the higher saturated the stone, the higher intensity of the peaks present.


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Figure 7. The ultraviolet-visible spectrum of kunzite.


Kunzite can be enhanced its color by irradiation and heating, while both natural and treated colors can fade with exposure to heat and bright light. As kunzite has high fragility and perfect cleavage in two directions, finishing the stone is a challenge even for the experienced cutter (Tuzlukov, 2020). Thus, buyers should be careful to store and wear this jewelry.



References

Mauthner M. (2011) The History of Kunzite and the California Connection. Rocks & Minerals, pp. 112-131.

Laurs B.M., Zwaan J.C., Breeding C.M., Simmons W.B., Beaton D., Rijsdijk K.F., Befi R., Falster A.U. (2008) Copper-bearing (paraÍba-type) Tourmaline from Mozambique. Gems & Gemology, Vol. 44, No. 1, pp. 4-30.

Tuzlukov V. (2020) The “Fragility of the Eternal” Kunzite: Origin, Cutting, and Identification, Gems & Gemology, Vol. 56, No. 2, pp. 303-306.



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