Infrared reflectance spectroscopy:

The infrared reflectance spectrum (figure 3) was collected from the stone's table and characterized the stone as zoisite. No investigation was conducted to look over the dimorphism of zoisite for determining if the stone is zoisite (orthorhombic) or clinozoisite (monoclinic).

UV-VIS-NIR spectroscopy:

Zoisite is trichroic and the studied stone does not depart from the general rule with its strong trichroism showing three colors: purple, light-pink and light-green-yellow. The UV-Vis-NIR spectra (figure 4) were collected by carrefully orienting the stone and using polarizing filters to separate the three polarization directions of the light through the crystal.

Even if all three spectra share common features at 422, 478/488, 522-534, 620, 720 and 760 nm, they significantly differ by the absorption bands intensity, explaining the strong trichroism. The 422, 522-534 and 720-760 nm bands are ascribed to the spin-allowed transitions of Mn³⁺ in the distorted octahedral M3 site, shoulder bands at 478 and 488 nm are ascribed to the spin-forbidden transitions of Mn³⁺. The 620 nm band is connected to V³⁺. The absorption edge towards higher energies below 400 nm is usually observed in V³⁺/Cr³⁺ zoisites.
In epidote structure, the Mn³⁺ ion (3d⁴) occupies the M3 site in octahedral coordination, a MO (Metal-Oxygen) site (Burns, 2005)^[3]. The energy levels of the spin-allowed bands of the collected spectra are drawn in the energy level diagram of figure 5. The distorted octahedral site leads e_g and t_2g groups to split into additional energy levels with the possibility of spin-allowed transitions. This explains the three bands instead of the only predicted one (one spin-allowed transition) in an ideal octahedral configuration where Mn³⁺ is unstable. Each energy level  correspond to the 3d orbitals (d_xy, d_xz, d_yz, d_z², d_x²-y²) and they are derived from the bands energies of the three polarized spectra by averaging them, they are relative to the e_g ground state. The stabilization energy of the t_2g orbitals split is δ₁ that is calculated as follows: δ₁ = 23,700 - 18,900 = 4,800 cm^-1 and the stabilization energy of the e_g orbitals split (caused by the Jahn-Teller effect) is δ₃ that equals to 13,510 cm^-1. The centre of gravity rules of the e_g and t_2g baricentres allow to calculate the crystal field splitting parameter Δ_o = 10D_q as follows: 23,700 - 2δ₁/3 - δ₃/2 thus Δ_o = 10D_q = 13,745 cm^-1. It is consitent with the This Δ_o = 13780 cm^-1 of the MK25 thulite sample (Langer et al., 2002)^[4].

Photoluminescence spectroscopy:

The photoluminescence spectrum (figure 6) was acquired with a 405 nm laser. Despite the power of the laser, the luminescence is rather weak. There is a weak emission at 469 nm related to REE³⁺ (Gaft et al., 2015)^[5], the 693 and 712 nm weak emissions are related to V²⁺ (Gaft et al., 2015)^[5]. The prominent 553 nm (18,080 cm^-1) emission is possibly connected to Mn³⁺ but the lack of litterature on the subject and the unexplained / unassigned corresponding energy level do not allow a firm conclusion. Additionally the 447 nm laser induces the same luminescence emissions (469, 553, 693 and 712 nm) as for the 405 nm laser but comparatively they are so weak. The 532 nm laser does not induce any luminescence as well as the SW- and LW-UV sources. From that, the 553 nm emission requires excitation energies greater than 450 nm (22,300 cm^-1) and lesser than 370 nm (27,000 cm^-1). Mn²⁺ may also be present in comparatively low concentration compared to Mn³⁺, the emission wavelength and its broadness are compatible with Mn²⁺ as well.

Conclusion:

This 0.97ct pink zoisite is undoubtly colored by Mn³⁺ as demonstrated by Visible spectroscopy. According to the thulite variety name definition, this gemstone can be qualified as 'zoisite var. thulite'. Is that naming so important ? In the trade, the thulite variety name has been in used for dacades and pertains to the massive form although the transparent pink gemstone is simply named pink zoisite.