## 4 The Example of the Green Stones
### The Nomenclature of the Green Stones
However, in the Chinese market, omphacite and kosmochlor \"rich members\" of the pyroxene group are often included in the term Fei Cui or, as per the Hong Kong trades, even \"pure\" omphacite and/or kosmochlor phases can be included under the Fei Cui umbrella term [96,97]. This overlapping of historical terminology with modern acceptation can generate misunderstandings that must be considered when cultural heritage samples and _objects d'art_ are identified. Another term used in the Green Stones panorama is Maw-Sit-Sit; it identifies a gem species corresponding to a green rock constituted by a variable mineralogical association and described for the first time by [PERSON] in 1965 [98]. In fact, Maw-Sit-Sit is the name of the Himalayan village close to Tawmaw (Myanmar), where this gem material is usually extracted. It must be noted that different authors reported different mineralogical associations characterizing the Maw-Sit-Sit. [PERSON] [99] described the Maw-Sit-Sit as a rock mainly composed of albite and Cr-jadeite; [PERSON] [100] identified nuclite and kosmochlor as the main constituents; [PERSON] and [PERSON] [101] found chromite, kosmochlor, and Cr-amphibole as the main minerals, and finally, [PERSON] [102] demonstrated a composition of albite and kosmochlore as main phases, with chromite, eckermannite, and nuclite as associated phases for Maw-Sit-Sit from Myanmar. This heterogeneity in the mineral associations reflects the variability of the parent rocks, derived from the complex metamorphic system of the Myanmar area. Considering the Green Stones, another big family eventually included is the crypto and micro-crystalline quartz species, such as chalcedony (chromium or chrysoprase varieties), jasper, and quartzite rocks. Indeed, this species can show several types of colors, includinggreen. Although the common basic unit consists of quartz crystals, the relatively significant heterogeneity of this class of gem materials must be noted. In fact, considering the jasper and chalcedony species, they are typically in hydrothermal (fluids precipitation product) and sedimentary environments [103; 104], while quartzite is a typical metamorphic product. As per the variety name, in the Cr-chalcedony variety, the green color is correlated with the chromium element as chromophore [105]; on the other hand, the characteristic \"apple green\" variety of the chalcedony species is the chrysoprase [106]. In addition to these, several other mineral phases are ascribable to Green Stones. Pyroxenes such as kosmochlor, diopside, and omphache have been already listed as associated minerals in jadeite or Maw-Sit-Sit, but they can also be identified as a single phase or dominant phase, characterizing the material analyzed. Moreover, belonging to Green Stones, other mineral phases can be listed, i.e., hydrogrossular and grossular, vesuvianite (californite, variety), or pumpellyite. Finally, a significant phase belonging to Green Stones is serpentine. By this term, three different polymorphs (minerals having the same chemical composition but different crystal structures) are identified: lizardite, antigorite, and chrysotile. While the first two are typically massive, the last one is of the fibrous variety. Chrysotile is unwillingly quite famous because it is listed as one of the six fibrous minerals identified by the law as \"asbestos\", and is hazardous to human health [107]. By this short overview of the main materials classified as \"Green Stones\" and their definition (summarized in Table 1), underlying their heterogeneity, the importance of the proper jade and related-to-jade materials identification for archaeological, cultural heritage studies, and antiquity trades becomes understandable [108]. A proper material identification represents the base of a good archaeometric work and, consequently, the base of archaeological or cultural heritage considerations. For example, the discussion about the origin or the technology applied for artifact creation is strictly related to the materials' properties and characteristics.