gems, jade, fei cui, pyroxene jade, jadeite, fei cui, omphacite, kosmochlor, fei cui hardness, Broken Bangle

Jade has a long and varied nomenclatural history, with its definition altered in the current age for practical and cultural reasons. Due to the discovery that many pyroxene jades are composed of various amounts of jadeite, omphacite and kosmochlor, the term “fei cui” has been proposed and widely accepted. It has been suggested that since the reported hardness of omphacite is lower than that of jadeite, a clear distinction should be made between omphacite- rich fei cui and other fei cui because of the potential long-term durability issues. Hardness also has a complicated history, as there are many factors to be considered when assessing the hardness of a material as well as its relation to scratch resistance. In this paper, the author examines these two topics and presents them in a simplified format based on empirical evidence and theoretical principles, while also considering the data available in literature.