Diamonds from the Mir Pipe (Yakutia): Spectroscopic Features and Annealing Studies

Mariana I Rakhmanova,Andrey Yu Komarovskikh,Alexander A Kalinin,Yuri N Palyanov,Olga P Yuryeva,Vladimir A Nadolinny

doi:10.3390/cryst11040366

Abstract

For this study, 21 samples of colorless octahedral diamonds (weighing 5.4–55.0 mg) from the Mir pipe (Yakutia) were investigated with photoluminescence (PL), infrared (IR), and electron paramagnetic resonance (EPR) spectroscopies. Based on the IR data, three groups of diamonds belonging to types IIa, IaAB, and IaB were selected and their spectroscopic features were analyzed in detail. The three categories of stones exhibited different characteristic PL systems. The type IaB diamonds demonstrated dominating nitrogen–nickel complexes S2, S3, and 523 nm, while they were less intensive or even absent in the type IaAB crystals. The type IIa diamonds showed a double peak at 417.4 + 418.7 nm (the 418 center in this study), which is assumed to be a nickel–boron defect. In the crystals analyzed, no matter which type, 490.7, 563.5, 613, and 676.3 nm systems of various intensity could be detected; moreover, N3, H3, and H4 centers were very common. The step-by-step annealing experiments were performed in the temperature range of 600–1700 °C. The treatment at 600 °C resulted in the 563.5 nm system’s disappearance; the interstitial carbon vacancy annihilation could be considered as a reason. The 676.5 nm and 613 nm defects annealed out at 1500 °C and 1700 °C, respectively. Furthermore, as a result of annealing at 1500 °C, the 558.5 and 576 nm centers characteristic of superdeep diamonds from São Luis (Brazil) appeared. These transformations could be explained by nitrogen diffusion or interaction with the dislocations and/or vacancies produced.

Highlights

The Mir pipe (Yakutia), discovered in 1955, was the second kimberlite pipe found in Russia
It is characterized by a high diamond content and a high number of gem-quality diamonds. Another interesting feature of this deposit is the abundance of low-nitrogen diamonds of type IIa, which are relatively rare in nature
Photoluminescence spectra were measured for bulk crystals at 80 K using a DFS-24 spectrometer (LOMO, Saint Petersburg, USSR); for excitation, we used the 313 nm line of a mercury DRT-230 lamp (LOMO, Saint Petersburg, USSR) and diode-pumped solid-state (DPSS) lasers emitting at 405 and 532 nm

Summary

Introduction

The Mir pipe (Yakutia), discovered in 1955, was the second kimberlite pipe found in Russia. It is characterized by a high diamond content and a high number of gem-quality diamonds. Another interesting feature of this deposit is the abundance of low-nitrogen diamonds of type IIa, which are relatively rare in nature. Diamonds from the Mir pipe have been thoroughly studied throughout the years. The mineral inclusions in diamonds from the Mir pipe correspond mostly to peridotite paragenesis of their host rocks [1,2,3,5]

Methods

Results

Conclusion