gems, jade, pyroxene jade, fei cui, Burma, jadeite, omphacite, geology, petrology

Jadeite considered as a rock: It is clearly evident, not only from the occurrence at Tammaw described elsewhere, but also from its distribution at a number of localities and from the size of the masses in which it is found, that jadeite must be regarded as a rock, and a definite type of rock, rather than as a mineral formed on a considerable scale in a single locality by some peculiar combination of circumstances unlikely to occur elsewhere. It appears to be a well-characterized variety of rock produced by the same laws that govern the formation of other rocks of similar type, and one whose occurrences may be expected to increase as geological exploration of the world continues. This position appears to the writer to be so self-evident that it requires no further argument, and it is also the view generally accepted. It may then fairly be asked whether jadeite itself, by its properties, structure, mineral composition, and chemical composition, offers evidence which, interpreted in light of our present knowledge of petrology, is sufficient to indicate its origin and petrographic position. The writer believes that this question can be answered in the affirmative and proposes to present the reasons for so believing.