Jadarite (LiNaSiB3O7OH) was discovered in Miocene carbonate-clastic sedimentary rocks of the Jadar lacustrine basin in western Serbia in 2004, with its formal definition as a new mineral in 2007 (Stanley et al., 2007; Whitfield et al., 2007; Borojević Šoštarić and Brenko, 2023). Jadarite’s initial claim to fame was its compositional similarity to the fictional substance “kryptonite” featured in “Superman” movies and TV shows. To date, the Jadar basin remains the only known occurrence of this mineral (Stanley et al., 2007; Borojević Šoštarić and Brenko, 2023). The Jadar deposit, also containing abundant searlesite (NaBSi2O5(OH)2), has the measured ore of 16.6 Mt grading 1.81 wt % Li2O and 13.4 wt % B2O3, as well as substantially larger indicated and inferred ores (Borojević Šoštarić and Brenko, 2023), representing one of the largest lithium resources in the world meeting the ever-increasing demand of this critical mineral for its applications in green technologies such as rechargeable Li batteries (Global Battery Alliance, 2019; U.S. Geological Survey, 2022).
This enormous Li-B deposit in the Jadar basin raises interesting questions about the condition and process for the formation of jadarite and the possible occurrences of this mineral in other lacustrine basins, with important implications for the discovery and sustainable development of similar Li-B deposits. Another salient feature of jadarite is its main chemical constituents of several light elements such as H, Li, and B, which are generally not detectable by conventional analytical techniques such as X-ray fluorescence (XRF) spectrometry and electron microprobe analysis (EMPA) and, therefore, may be overlooked during routine analyses. Therefore, the development and application of other analytical techniques such as laser Raman spectroscopy are also important for the detection of jadarite in the quest for the sustainable development of the critical Li resource.
The crystal structure of jadarite consists of a tetrahedral layer of corner-sharing LiO4, SiO4, and two BO4 groups parallel to (010), which is decorated with triangular BO3 groups (Fig. 1; Whitfield et al., 2007). One of the two crystallographically distinct BO4 groups containing a long bond of 1.602 Å (Whitfield et al., 2007) deviates significantly from the tetrahedral configuration and is better described as an OBO3 pyramid (Fleet and Liu, 2001; Zhou et al., 2016). The Na ion occurs at a distorted octahedral site between the tetrahedral layers, while the H atom is located at the apex of the BO3 group and is involved in a weak hydrogen bond between the tetrahedral layers (Whitfield et al., 2007). Comboni et al. (2022) performed an in situ single-crystal and powder synchrotron X-ray diffraction study of jadarite under a hydrostatic pressure of up to 20 GPa and reported a first-order, iso-symmetric, reconstructive phase transition with a volume reduction of ∼ 3 % between 16.57(5) and 17.04(5) GPa.
This contribution reports on the results of our hydrothermal synthesis of jadarite in the Li2O-Na2O-B2O3-SiO2-NaCl-H2O system under sedimentary-diagenetic conditions (temperatures of 100-230 ∘C and pH = 4-12). Synthetic jadarite was then characterized by a combination of analytical techniques from powder X-ray diffraction (PXRD) analysis to Fourier transform infrared (FTIR) spectroscopy, laser Raman spectroscopy, and synchrotron Li and B K-edge X-ray absorption near-edge structure (XANES) spectroscopy. These new data of synthetic jadarite are then compared with those available for its natural counterpart (e.g. PXRD and FTIR; Stanley et al., 2007; Comboni et al., 2022). In addition, first-principles theoretical calculations have been made to add to the interpretation of these experimental data (i.e. assignments of FTIR and Raman vibrational peaks, as well as the measured Li and B K-edge XANES features). Moreover, the new data of jadarite synthesis are discussed in the context of its formation conditions and implications for the exploration of Li-B deposits in sedimentary basins.