Rare asteriated trapiche-like diamond
The photomicrograph below shows a rare near-colorless asteriated trapiche-like diamond (0.07 ct, type IaA>>B, Hydrogen- and Nitrogen-rich) that possess some dark grey growth sectors forming an unusual Maltese cross-like pattern. This pattern is the result of the presence within the diamond of numerous sub-microscopic grey-to-black particles geometrically arranged in the diamond [1]Massi L. (2005) Studies of defects in brown and hydrogen-rich diamonds, PhD thesis, University of Nantes – France, 372 pages (PDF).
This sample is inert under SW-UV light whereas the near-colorless matrix shows a faint yellow fluorescence under LW UV light, but without phosphorescence in both cases.
This trapiche-like diamond is typically the result of a simultaneous mixed growth of cuboid and octahedral sectors [2]Howell D., Griffin W. L., Piazolo S., Say J.M., Stern R.A., Stachel T., Nasdala L., Rabeau J.R., Pearson N.J. and O’Reilly S.Y. (2013) A spectroscopic and carbon-isotope study of mixed-habit diamonds: Impurity characteristics and growth environment, American Mineralogist vol. 98, No. 1, pp. 66-77. One can even clearly see on the picture above three striking concentric cuboid layers circling the cross, layers also visible in that diamond that is there resulting from a pure cuboid growth (thus not showing any cross-shaped pattern).
This star-shaped pattern formed within the diamond is the result of light-scattering defects (photomicrograph below) being present in the cuboid growth sectors but absent in the octahedral sectors [1]Massi L. (2005) Studies of defects in brown and hydrogen-rich diamonds, PhD thesis, University of Nantes – France, 372 pages & [3]Lang A.R. (1974) On the growth-sectorial dependence of defects in natural diamonds, Proceedings of The Royal Society A, vol. 340, No. 1621..
As it is often the case, taking a little bit of time to observe our gems under a microscope can be a very rewarding activity as, beyond the pure artistic aspect of it – gemstones are also incredibly beautiful when viewed from within – one can even have the chance to discover something truly unusual, and why not find an inclusion that has never been described before, that would be worth sharing with the greatest number, as I do here with this blog.
Let’s all go back to our microscopes 😉
To go further:
(Literature the reader might be interested to read to get more technical information on the topic covered in this blog post)
- Ragozin A., Zedgenizov D., Kuper K., Kalinina V. and Zemnukhov A. (2017) The Internal Structure of Yellow Cuboid Diamonds from Alluvial Placers of the Northeastern Siberian Platform, Special issue of Crystals: « Diamond Crystals », 7(8), 238.
- Rondeau B., Fritsch E., Guiraud M., Chalain J-P. and Notari F (2004) Three historical ‘asteriated’ hydrogen-rich diamonds: growth history and sector-dependent impurity incorporation, Diamond & Related Materials vol. 13, pp. 1658– 1673.
- Zedgenizov D.A., Kalinina V.V., Reutsky V.N., Yuryeva O.P. and Rakhmanova M.I. (2016) Regular cuboid diamonds from placers on the northeastern Siberian platform, Lithos, 265, 125–137.
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