TY - JOUR

T1 - Why Tolbachik diamonds cannot be natural

AU - Litasov, Konstantin D.

AU - Kagi, Hiroyuki

AU - Bekker, Tatyana B.

AU - Makino, Yoshiki

AU - Hirata, Takafumi

AU - Brazhkin, Vadim V.

N1 - Publisher Copyright: © 2021 Walter de Gruyter GmbH, Berlin/Boston. Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

PY - 2021/1/27

Y1 - 2021/1/27

N2 - Taking into account recent publications, we provide additional comprehensive evidence that type Ib cuboctahedral diamonds and some other microcrystalline diamonds from Kamchatka volcanic rocks and alluvial placers cannot be natural and undoubtedly represent synthetic materials, which appear in the natural rocks by anthropogenic contamination. The major arguments provided in favor of the natural origin of those diamonds can be easily disproved. They include the coexistence of diamond and deltalumite from Koryaksky volcano; coexistence with super-reduced corundum and moissanite, Mn-Ni silicide inclusions, F-Cl enrichment and F/Cl ratios, and carbon and nitrogen isotopes in Tolbachik diamonds, as well as microtwinning, Mn-Ni silicides, and other inclusions in microcrystalline diamond aggregates from other Kamchatka placers. We emphasize the importance of careful comparison of unusual minerals found in nature, which include type Ib cuboctahedral diamonds and super-reduced phase assemblages resembling industrial slags, with synthetic analogs. The cavitation model proposed for the origin of Tolbachik diamonds is also unreliable since cavitation has only been shown to cause the formation of nanosized diamonds only.

AB - Taking into account recent publications, we provide additional comprehensive evidence that type Ib cuboctahedral diamonds and some other microcrystalline diamonds from Kamchatka volcanic rocks and alluvial placers cannot be natural and undoubtedly represent synthetic materials, which appear in the natural rocks by anthropogenic contamination. The major arguments provided in favor of the natural origin of those diamonds can be easily disproved. They include the coexistence of diamond and deltalumite from Koryaksky volcano; coexistence with super-reduced corundum and moissanite, Mn-Ni silicide inclusions, F-Cl enrichment and F/Cl ratios, and carbon and nitrogen isotopes in Tolbachik diamonds, as well as microtwinning, Mn-Ni silicides, and other inclusions in microcrystalline diamond aggregates from other Kamchatka placers. We emphasize the importance of careful comparison of unusual minerals found in nature, which include type Ib cuboctahedral diamonds and super-reduced phase assemblages resembling industrial slags, with synthetic analogs. The cavitation model proposed for the origin of Tolbachik diamonds is also unreliable since cavitation has only been shown to cause the formation of nanosized diamonds only.

KW - cavitation

KW - Diamond

KW - HPHT synthesis

KW - Kamchatka

KW - metal catalyst

KW - silicide

KW - super-reduced phases

UR - http://www.scopus.com/inward/record.url?scp=85099362648&partnerID=8YFLogxK

U2 - 10.2138/am-2020-7562

DO - 10.2138/am-2020-7562

M3 - Article

AN - SCOPUS:85099362648

VL - 106

SP - 44

EP - 53

JO - American Mineralogist

JF - American Mineralogist

SN - 0003-004X

IS - 1

ER -