Gemological characteristics of Mong Hsu rubies.8

Contexts in source publication

Context 1

... Properties. The distinctive color distri- bution in Mong Hsu rubies is also reflected in some of their gelnological properties (table 1). ...

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... Properties. We found the variations in refractive index ainong the different sainples to be unusually high for both the ordinary and extraordi- nary rays, with a slightly variable birefringence between 0.008 and 0.010 (see table 1). A similar large variation in R.I.'s was reported by Smith and Surdez (1994) for rubies froin Mong Hsu, and was recently describcd for rubies froin Malawi that revealed highly variable ainounts of trace elements, especially chroiniuin ( Bank et al., 1988). ...

Context 3

... depending on the orientation of the table facet with respect to the optical axis and the portion of the original crystal the table encompass- es, different refractive indices are possible. If the table facet is largely confined to one single growth zone (see "Microscopic Features" below and boxes A and B), sharp shadow edges are observed for the ordinary and the extraordinary rays on the refrac- tometer (table 1). This is often the case for samples with table facets cut parallel to the c-axis or for samples with small cores. ...