English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Kaminsky et al. (2019) described enigmatic polycrystalline diamond from the placers on Aynyn River at Kamchatka peninsula and named them “kamchatite.” The samples were picked up from the mineral separates in the alluvial deposits. They are up to 1 mm in size and have a rounded shape. Octahedral and irregular diamond crystallites (2–40 mm in size) occupy about 50 vol% of the aggregates. The matrix cementing the diamond crystals consists of Ca5(Si2O7)(CO3)2 tilleyite, SiC, Fe-Ni-Mn-Cr silicides, native silicon, graphite, calcite, and some amorphous material. Three types of composition of the amorphous materials can be recognized from transmission electron microscopy observations: tilleyite-like material, carbon, and SiO2. Another related finding of porous carbonado-like diamond was reported earlier for Avacha volcano (Gorshkov et al. 1995; Kaminsky et al. 2016). In this case, diamond crystallites have a size of 1–10 mm and contain minor interstitial materials represented by Mn-Ni-Si-Fe alloys, native Mn, WC, B4C, SiO2 (amorphous and tridymite); native Si and SiC. The authors suggested the natural origin of these diamonds during volcanic eruptions via a gas phase condensation with the possible participation of strongly reduced CH4-H2 fluid during their formation (Kaminsky et al. 2019). The process can be similar to carbon vapor deposition (CVD) synthesis of diamonds. Recently we have found very strong evidence for the artificial origin of type Ib diamonds crystals (up to 0.7 mm in size) found in the volcanic rocks of Tolbachik volcano and peridotites and chromitites worldwide (Litasov et al. 2019b, 2019c; Pokhilenko et al. 2019). In Tolbachik, diamonds were found in the ash-like crusts and scabs on the solidified lava flow. They contain Mn-Ni metallic inclusions (with impurities of Fe, Cr, Ti, and Si), which generally resemble the chemical composition of the standard Mn60Ni40 catalyst for the diamond synthesis in Russia. Most diamonds from Tibet, Ural, Turkey, and Albania ophiolites contain metallic Ni-Mn-Co inclusions, which resembles standard Ni70Mn25Co5 catalyst for the diamond synthesis in China. Although there is an ongoing discussion on the subject (Yang et al. 2020; Litasov et al. 2020), our point of view remains unchanged and is supported by the mentioned similarities with the industrial catalysts.

american mineralogist

“Kamchatite” diamond aggregate from northern Kamchatka, Russia: New find of diamond formed by gas phase condensation or chemical vapor deposition—Discussion