GE POL Diamonds: Before and After
As is typical for type iia diamonds, all of the samples studied showed tatami and banded extinction patterns with first-order interference colors when viewed between crossed polarizers. Photomicrograph by Christopher P. Smith.
This study of type iia GE POL diamonds before and after HPHT annealing by GE significantly expands on their characterization. The color change was dramatic: from the N-O range through Fancy Light brown before, to D-H after. However, there was little change to the inclusion, graining, and strain as a result of HPHT exposure. Photoluminescence (PL) studies—conducted at liquid helium, liquid nitrogen, and room temperature in the 245-700 nm range—identified a significant reconfiguration of the lattice involving substitutional impurities, vacancies, ad interstitials.
Key regions of PL activity included the areas of the N3, H3, and N-V centers. X-ray topography identified the extent of lattice distortion. Cathodoluminescence may help establish that a diamond is not HPHT annealed. A distinction between non-enhanced and color-enhanced type iia diamonds can be made through a combination of observations and features.
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