CLIPPIR

CLIPPIR diamonds are a geologically distinct diamond family. They have a set of unusual characteristics that set them apart from other more common kinds of diamonds. The name CLIPPIR is relatively new. For many years they have been loosely referred to as "type IIa" because this is the most readily quantifiable characteristic that appears to distinguish them. In detail, however, these special diamonds cannot be unambiguously described on the basis of "type" (nitrogen content) alone. For that reason, this family of diamonds was given a more descriptive name.

The CLIPPIR acronym, first appearing in the 2016 Science paper on this topic, encompasses diamonds with characteristics like the historic 3106 carat Cullinan diamond. Most examples of large, colourless (D-colour), type IIa diamonds are part of the CLIPPIR variety. In fact, the initial recognition of this population stems from the many claims in the gem trade that larger, higher-quality diamonds have a greater tendency to be type IIa. These large type IIa diamonds have very few inclusions and consequently result in polished diamonds with high clarity grades.

Some CLIPPIR diamonds are not type IIa, and some type IIa diamonds are not CLIPPIR's. Rather than relying on nitrogen (diamond type) alone to try to define this variety of diamond, the CLIPPIR acronym appeals to the set of characteristics that set these diamonds apart as being unusual. CLIPPIR diamonds tend to be large, inclusion poor, and relatively pure (almost always type IIa), and in their rough state they are irregularly shaped and significantly resorbed. It is important to note that these key characteristics distinguish the population as a whole. On an individual basis, some variance in CLIPPIR diamond characteristics should be expected. For instance, there are certainly many examples of smaller CLIPPIR diamonds (<1 carat) or examples containing more inclusions. It should also be noted that the specific features of CLIPPIR diamonds may overlap with other kinds of sublithospheric diamonds, such as type IIb's or those diamonds typical of Juina, Brazil. Some diamonds may well be the result of combined or transitional diamond-forming processes.

Read more in my summary HERE

Three interesting observations from the prevalent metallic inclusions in CLIPPIR diamonds

Key papers:

• Smith, E.M., Ni, P., Shirey, S.B., Richardson, S.H., Wang, W., Shahar, A. (2021) Heavy iron in large gem diamonds traces deep subduction of serpentinized ocean floor. Science Advances, 7:eabe9773, 10.1126/sciadv.abe9773 (open access)

• Smith, E.M., Shirey, S.B., and Wang, W. (2017) The very deep origin of the world’s biggest diamonds. Gems & Gemology, 53: 388-403. 10.5741/gems.53.4.388 Free access HERE

• Smith, E.M., Shirey, S.B., Nestola, F., Bullock, E.S., Wang, J., Richardson, S.H. and Wang, W. (2016) Large gem diamonds from metallic liquid in Earth’s deep mantle. Science, 354: 1403-1405. 10.1126/science.aal1303 Free through link HERE

• Moore, A. E. (2014) The origin of large irregular gem-quality Type II diamonds and the rarity of blue Type IIb varieties. South African Journal of Geology, 117(2), 219-236. 10.2113/gssajg.117.2.219

• Gurney, J. J. and Helmstaedt, H. H. (2012) The origins of Type IIa diamonds and their enhanced economic significance. 10th International Kimberlite Conference, Extended Abstract No. 10IKC-123, 1-6.

• Bowen, D. C., Ferraris, R. D., Palmer, C. E. and Ward, J. D. (2009) On the unusual characteristics of the diamonds from Letšeng-la-Terae kimberlites, Lesotho. Lithos, 112S(0), 767-774. 10.1016/j.lithos.2009.04.026

• Moore, A. E. (2009) Type II diamonds: Flamboyant megacrysts? South African Journal of Geology, 112(1), 23-38. 10.2113/gssajg.112.1.23