Hongquiite

Mystery:
Is this mineral TiO or TiC (latter being end-member of khambravateit)?
There is conflicting info on the web.
Seems evidence mounts for TiO.

Simple cubic rock salt structure, so much is sure.

TiO

• mindat.org Hongquiite – Mohs 3.5 (odd, seems a bit soft)
• webmineral.com Hongquiite – Mohs 5.0 to 6.0
• ins-europa Hongquiite
• 2011 – Chemical modification of titanium immersed in hydrogen peroxide using nanosecond pulsed fiber laser irradiation
• 2021 – Porous micro/nano structured oxidic titanium surface decorated with silicon monoxide
• https://www.chemicalbook.com/synthesis/titanium-monoxide.htm
• https://it.wikipedia.org/wiki/Hongquiite
• https://athena.unige.ch/minfich?id=HONGQUIITE
• https://www.chemicalbook.com/ChemicalProductProperty_EN_CB6283368.htm
• https://www.chemicalbook.com/synthesis/titanium-monoxide.htm
• 1985 – The heat-capacity of ilmenite and phase equilibria in the system Fe-T-O
• https://www.researchgate.net/figure/Graphical-illustration-of-two-dominant-phases-formed-in-a-multi-Ti-oxide-phased_fig2_282870768
• https://de.wikipedia.org/wiki/Systematik_der_Minerale_nach_Dana/Oxide_und_Hydroxide (hongquite liste as oxide)
• https://de.wikipedia.org/wiki/Monteponit & https://de.wikipedia.org/wiki/W%C3%BCstit & https://de.wikipedia.org/wiki/Manganosit & https://de.wikipedia.org/wiki/Bunsenit & https://de.wikipedia.org/wiki/Thortveitit & https://de.wikipedia.org/wiki/Periklas (hongquite liste as oxide)

TiC

• German mineral atlas Hongquiite Mohs 5.5 to 6.0
• euromin Hongquiite Mohs 5.5 to 6.0 (odd, TiC should be harder)
• https://de.wikipedia.org/wiki/Haxonit https://de.wikipedia.org/wiki/Lapis-Systematik (hongquite listed among carbides)

TiC as khamrabaevite

• Wikipedia: Titanium carbide Mohs 9.0 to 9.5

Related

• Titanium

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• Khamrabaevite TiC
• Osbormite TiN
• Hongquiite TiO (this pager here)

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Same nonmetallide combinations but with silicon. These are all not simple cubic
hinting on limits on Si vs Ti substitutability.

• Moissanite SiC
• Nierite Si₃N₄
• SiO₂: Quartz, Stishovite, Seifertite, …