|By Bruce L. Harding
Holden, Massachusetts, USA
|Table of content
| The pavilion and bezel slopes commonly recommended
for faceting are the result of trial-and-error and human judgment.
This explains why references differ in their recommendations.
Trial-and-error is an effective way
to solve complex problems until a better way comes along, but it usually
finds only the best solution in the range of experimentation. Other
good solutions may exist – beyond the bad ones – but are found only
by accident. This has been as true in faceting as in many other scientific
Inspired by an exceptionally brilliant
but strangely-cut emerald, the writer went in search of these other
solutions and found that there are indeed two ore three areas of good
design for each gem material.
This article presents the first and
most important result of that search – charts for each of the common
faceting materials which show areas of good and bad pavilion and bezel
slope combinations; it also defines maximum and minimum table sizes
briefly (more later). The faceter can choose from the various «good»
areas according to what he thinks is best or to suit the limited proportions
of his rough material.
The text describes the formation of
these charts so that you can understand them better. Technical details
are omitted; it is assumed that you are either familiar with gemology
optics or don`t care. The mathematics involved are quite simple but
are deferred to an appendix for those who care to understand them
or who may need to create additional charts.