Gem News International Gems & Gemology, Spring 2025, Vol. 61, No. 1

New Deposit of Pezzottaite from Madagascar

Alexander A. Goodsuhm, Nathan Renfro, and Wim Vertriest

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Figure 1. A faceted pezzottaite, measuring approximately 6 × 4 mm, with a group of rough (largest piece ~25 mm in diameter) exhibiting purplish pink to red color from the Vakinankaratra region of Madagascar. Photo by Nathan Renfro; courtesy of Lamine Kakro and Yianni Melas.
 
Figure 1. A faceted pezzottaite, measuring approximately 6 × 4 mm, with a group of rough (largest piece ~25 mm in diameter) exhibiting purplish pink to red color from the Vakinankaratra region of Madagascar. Photo by Nathan Renfro; courtesy of Lamine Kakro and Yianni Melas.
Figure 2. Rough samples of pezzottaite (5.02 carats total) acquired at the AGTA show from the parcel shown in figure 1. The difference in appearance is due to the small size of the acquired samples and resultant lower saturation. Photo by Annie Haynes.
 
Figure 2. Rough samples of pezzottaite (5.02 carats total) acquired at the AGTA show from the parcel shown in figure 1. The difference in appearance is due to the small size of the acquired samples and resultant lower saturation. Photo by Annie Haynes.

Pezzottaite is a rare, purplish pink gemstone and a mineral of the beryl group, characterized by high lithium and cesium contents (Cs(Be2Li)Al2(Si6O18)). In Tucson, the authors encountered a parcel of highly saturated purplish pink to red pezzottaite (figure 1) from a new deposit in Madagascar with color noticeably more saturated than earlier known production from the Sakavalana granitic pegmatite near Ambatovita (B.M. Laurs et al., “Pezzottaite from Ambatovita, Madagascar: A new gem material,” Winter 2003 G&G, pp. 284–301). The stones ranged in sizes from as small as 2 mm to tabular crystals approximately 25 mm in diameter and were reportedly from the Sahatany Valley in the Vakinankaratra region of central Madagascar. Rough samples of the material (5.02 carats total) were acquired from Lamine Kakro and Yianni Melas at the AGTA show and later analyzed at GIA (figure 2).

Standard gemological testing indicated refractive indices from ne = 1.600–1.611 and no = 1.610–1.621 and specific gravity from 3.05–3.14. The stones had a pinkish purple hue with medium tone and moderate to strong saturation. All samples demonstrated strong pleochroism, showing purplish pink when viewed perpendicular to the c-axis and reddish orange when viewed parallel to the c-axis. Crystallographic orientations were determined visually for samples with preserved crystal form. Three of the samples showed uniaxial interference figures in the polariscope, and all samples were inert under short-wave and long-wave fluorescence. These gemological properties were consistent with pezzottaite, although the color was much more intense than that of previously observed stones. Microscopic examination revealed numerous fractures and small fluid inclusions, though the samples were generally free of foreign mineral inclusions.

Figure 3. UV-Vis-NIR absorption spectra of pezzottaite from Vakinankaratra, Madagascar. The difference in the spectra based on orientation explains the pleochroism observed in the pezzottaite samples.
 
Figure 3. UV-Vis-NIR absorption spectra of pezzottaite from Vakinankaratra, Madagascar. The difference in the spectra based on orientation explains the pleochroism observed in the pezzottaite samples.
Table 1. Chemical analyses of pezzottaite (determined by LA-ICP-MS) from Vakinankaratra, Madagascar.
 

Raman spectroscopy confirmed the identity of the material as pezzottaite by an intense peak at ~1100 cm–1, which is not present in beryl. Fourier-transform infrared spectroscopy showed features associated with water in the crystal structure, which confirmed its distinction from red beryl despite having a similar color. Ultraviolet/visible/near-infrared (UV-Vis-NIR) spectra were collected parallel and perpendicular to the crystallographic c-axis (figure 3), with differences based on orientation matching observations of moderate to strong pleochroism and no evidence of dyes altering the color. Elemental concentrations were determined by laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) analysis. Three spots were ablated on each sample, for a total of 18 analyses: Cs2O ranged from 10.88–16.79 wt.% in the samples, while Li2O ranged from 1.94–2.51 wt.% (table 1).

Standard gemological testing and advanced testing both confirmed the identity of the samples as pezzottaite. These samples are remarkable due to their vivid saturation, which makes them unique compared to the previously available pezzottaite.

Alexander Goodsuhm is a research associate, and Nathan Renfro is senior manager of colored stone identification, at GIA in Carlsbad, California. Wim Vertriest is manager of field gemology at GIA in Bangkok.