Coesite inclusions in diamonds of Yakutia

The results of the study of diamonds with inclusions of high-pressure modification of SiO2 (coesite) by Raman spectroscopy are reported. It is established that the octahedral crystal from the Zapolyarnaya pipe is characterized by the highest residual pressure (2.7 +/- 0.07 GPa). An intermediate value of this parameter (2.1 +/- 0.07 GPa) was obtained for a crystal of transitional habit from the Maiskaya pipe. The minimal Raman shift was registered for coesite in diamond from the Komsomol'skaya-Magnitnaya pipe and provided a calculated residual pressure of 1.8 +/- 0.03 GPa. The residual pressures for crystals from the placer deposits of the Kuoika and Bol'shaya Kuonamka rivers are 2.7 +/- 0.07 and 3.1 +/- 0.1 GPa, respectively. Octahedral crystals were formed in the mantle at a higher pressure than rhombododecahedral diamonds.