## 4 The Example of the Green Stones
### Classical Gemological and Mineralogical Properties
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Mineral Phase** & **Chemical Formula** & **Group/Family** & **Crystal System** \\ \hline Jadeite & NaAl[Si\({}_{2}\)O\({}_{6}\)] & Clinopyroxene & Monocline \\ \hline Actinolite 1 & Ca\({}_{2}\)(Mg,Fe)\({}_{5}\)[Si\({}_{2}\)O\({}_{6}\)](OH)\({}_{2}\) & & \\ Tremolite 1 & Ca\({}_{2}\)Mg\({}_{5}\)[Si\({}_{2}\)O\({}_{6}\)](OH)\({}_{2}\) & & \\ \hline Lizardite 2 & & & Trigonal \\ Antigorite 2 & Mg\({}_{3}\)[Si\({}_{2}\)O\({}_{5}\)](OH)\({}_{4}\) & Trioctahedral Phyllosilicate & Monocline \\ Chrysotile 2 & & & Orthorhombic \\ \hline Albite 3 & Na[AlSi\({}_{3}\)O\({}_{8}\)] & Tetosilicate, Plagioclase & Triclinic \\ Kosmochlor 3 & NaCr[Si\({}_{2}\)O\({}_{6}\)] & Pyroxene & Monocline \\ Chromite 3 & Fe\({}^{2+}\)Cr\({}_{2}\)O\({}_{4}\) & Oxides, Spinels & Cubic \\ Eckermannite 3 & Na\({}_{3}\)Mg\({}_{4}\)Al[Si\({}_{6}\)O\({}_{22}\)](OH)\({}_{2}\) & Amphibole & Monocline \\ Natrolite 3 & Na\({}_{16}\)[Al\({}_{16}\)Si\({}_{24}\)O\({}_{80}\)]\(\cdot\)16H\({}_{2}\)O & Tetosilicate, Zeolite & Orthorhombic \\ \hline Hydrogrossular & Ca\({}_{3}\)Al\({}_{2}\)(Si\({}_{3}\)O\({}_{12}\))\(\cdot\)(H\({}_{2}\)O)\({}_{2\text{-}6}\) & Nesosilicate, & \\ Garnet & Cubic & & \\ Vesuvianite & (Ca,Na)\({}_{19}\)(Al,Mg,Fe)\({}_{13}\)(SiO\({}_{4}\))\({}_{10}\)(Si\({}_{2}\)O\({}_{7}\))\({}_{4}\) & Sorosilicate & Tetragonal \\ (OH,F,O)\({}_{10}\) & & & \\ \hline Diopside & CaMg\({}_{5}\)Si\({}_{2}\)O\({}_{6}\) & Clinopyroxene & Monocline \\ \hline Omphacite & (Ca,Na)(Mg,Fe\({}^{2+}\),Fe\({}^{3+}\))[AlSi\({}_{3}\)O\({}_{8}\)] & Clinopyroxene & Monocline \\ \hline Pumpellyite & Ca\({}_{2}\)MgAl\({}_{2}\)(Si\({}_{2}\)O\({}_{7}\))(SiO\({}_{4}\))(OH)\({}_{2}\)\(\cdot\)H\({}_{2}\)O & Sorosilicate & Monocline \\ \hline Quartz 4 & SiO\({}_{2}\) & Tetosilicate & Trigonal \\ \hline \hline \end{tabular}  
* Main mineral phases (pure end members) constituting nephrite gemological species. 2 Serpentine polymorphs, particularly the chrysotile is the fibrous variety of the mineral. 3 Main mineral phases constituting Maw-Sit-Sit variety. 4 Main mineral phase constituting chalcedony species.  
\end{table} 
Table 3: Main mineralogical characteristics of Green Stones species here discussed [96; 113; 114]. For the series, the chemical formula of the end member/pure phase has been reported. crystallization. In this condition of regional metamorphism, gabbro rocks can show veins rich in jadeite-pumpellyite association (Figure 2b) [114]. This example can help to understand why the determination of geographic origin in Green Stones is so complex: not only different mines can produce similar materials, but also differences in terms of chemical and mineralogical distribution can be found within the same vein [90]. Moreover, from a multidisciplinary point of view, the knowledge of the geological process and the petrographic identification of the mining areas are necessary information for the geographic origin hypothesis [115]. The same consideration can be applied to amphibes and serpentine, and both correlate with metamorphic processes. Serpentines, in particular, are typical products of the transformation of ultramafic rocks by a hydrothermal metamorphic system, while nephrite requires not only the conditions for actinolite-tremolite crystallization but also the condition for its characteristic texture (Figure 2c). Figure 2c, in particular, shows the sample detail where the interlocking mass of granular and acicular crystals without a preferred orientation are well visible. Regarding the nephrite genesis, [PERSON] [116], describing for example the ultramafic complex of East Sayan, reported nephrite veins formation at the base of the ultramafic members of the ophthalmic nappes, as a consequence of the metamorphism and metasomatis resulting from frictional heating at the block-matrix contacts. The hydrogrossular and grosular (Figure 3a) are garnets crystallized typically from the thermal metamorphic process applied to limestone.