The Indian Gemological Institute – Gem testing Laboratory, Delhi (India) examined a 1.01 ct Yellowish brown, pear mixed cut, Natural Diamond (Figure 1). Infra Red spectroscopy revealed features as found in type 1aA diamond, with slight absorption peak of hydrogen impurity. In microscopic examination, the diamond was observed to be profuse with unusual flaky, disc like translucent inclusions, lying in planes (Figure 2).
Flakes of some unknown identity were evenly scattered on planes parallel to each other in 4 different directions. These four directional intersecting planes were probably parallel to octahedral faces. These flake/platy inclusions were forming patches/groups along 4 directional planes. Although most of the flakes were round in shape, few flakes were showing cross section of hexagonal shape (Figures 3 and 4). Crystals (Figure 5) and indented natural with growth markings and striations on rough diamond skin, left unpolished, were also observed under microscopic examination (Figures 6 and 7).
Diamond View imaging of the diamond from crown side showed a yellowish green fluorescence pattern with growth features as found in natural diamonds. On crown side, few blue zones, inert irregular patches and some chalky blue fluorescence patches were also observed (Figure 1d). Chalky patches on table showed chalky blue phosphorescence too, while other yellowish green fluorescence portion of diamond did not show phosphorescence (Figures 2d and 2.1d).
Diamond View imaging of the diamond from pavilion side exhibited unusual fluorescence pattern of blue and yellowish green fluorescence regions/zones. Inert broad bands were present around green fluorescence zones, separating them from blue fluorescence zones (Figure 3d). Unusual inert circular patches/spots were visible confined to blue fluorescence zones only. A net like square zone, lookalike QR Code (Figure 4d), was present in the yellowish green fluorescence area on the pavilion side of the diamond, exhibiting some faint chalky blue fluorescence portions.
Chalky blue fluorescence portions were so pale that they were appearing almost inert. These faint chalky blue portions also showed strong phosphorescence in Diamond View (Figure 4.1d). It was impossible to assert a direct correlation between the flaky inclusions and these inert circular patches/spots being these flaky inclusions abundantly present in the whole stone, while these inert circular patches were confined to specific portion i.e. to the portion showing blue fluorescence in Diamond View. Moreover those flaky inclusions can be seen shining through the yellowish green fluorescence zone, a confirmation that flaky inclusions and inert circular patches in blue fluorescence zone are not related to each other.
*Meenakshi Chauhan is Manager (Gemologist) at IGI-GTL in Delhi (India)
Article by Meenakshi Chauhan*, published on IGR – Italian Gemological Review #3, January 2018.
