Occasionally inclusions in cut diamonds are so orientated that they are reflected several times through the neighboring facet. For instance an inclusion which is situated in the centre of the stone-directly above the culet can be reflected eight times through. the pavilion main facets and sixteen times through pavilion girdle facets. Also crown facets often show a reflection which make localization more difficult and sometimes the multiple reflections give rise to doubts in the mind of the observer as to the exact number of inclusions.
The reflected inclusion appears several times as exactly the same shape. This alone is already proof that it is only a single inclusion, as several twin-like inclusions appear very rarely in diamond (172a). It is also advisable to position the facet above the doubtful inclusion perpendicular to the viewing direction, thus eliminating all reflections (Fig 172 a and b, 173 a and b).
Cracks are an exception as they can appear differently
when viewed through crown or pavilion. From one position the grader sees
the edge of the crack:
From another the area, which presents two totally different pictures,
which might give the mistaken impression of two different inclusions.
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| Fig 172 a A crystal inclusion on a facet edge with double reflection | Fig 172b As Fig 172a seen through pavilion |
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| Fig 173 a A crystal inclusion with multiple reflection | Fig 173 b As Fig 173 a seen through pavilion |
As already mentioned several reflected inclusions are graded lower than the single inclusion. Although in reality only few inclusions are present in the diamond, the multiple reflection diminish its transparency and brilliance. Often reflected inclusions are made readily visible by the naked eye, while magnification is needed to find the actual cause.
| Differentiating between surface features and inclusions | Representation of internal and external features in the identity diagram |