Découverte et observations des grenats trapiches

In gemmology, it is rare for varieties or crystallization of as-yet-unknown gems to appear of sufficient size, quality and quantity to be found on the market. The recent discovery of high-quality trapeze grossular garnets from China has therefore aroused particular interest among gemmologists and collectors who have been able to acquire them, as was the case for one of the authors of this article. These trapiche garnets were the subject of a study (Wang et al., 2025) published during the preparation of this article. The results on our samples corroborate the results and observations of this study. However, some of our observations and analyses shed light on the crystal growth of these garnets. For example, the trapiche pattern is not a six-branch pattern but the superposition of two three-branch patterns offset by an angle of 60°. A study of the luminescence of our samples showed a relatively intense orange luminescence under long ultraviolet light (365 nm), mainly associated with the presence of Mn2+. This attribution is correlated with the presence of absorption bands characteristic of this ion in the UV-visible range. Other emissions can also be attributed to the presence of Nd3+ or Dy3+, for example.