Organic gemstone-like compound

Organic gemstones shall include all gemstones that ...

• ... do not contain metals but only light non-metallic elements
• ... do contain carbon

Organic gemstones typically ...

• ... contain volatile elements (carbon, nitrogen)
• ... are combustible.
• ... become unstable if too much oxygen (or sulfur) is mechanosynthetically added

List of organic gemstone compounds (attempting exhaustiveness)

The options are rather limited so it seems here (for once) one quickly can arrive at a quite exhaustive list of the most basic possible structures.
As always on this wiki: The heavier more scarce elements (Arsenic, Selenium, ...) are excluded for materials for eventual large scale structural use.

• C Diamond
• C Lonsdaleite
• β-C₃N₄ Beta carbon nitride – (possibly a fire hazard)
• C_?P_? Likely some carbon phosphides (at least sheets) – eventual health hazard due to direct carbon phosphorus bonds (common in toxins)

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Perhaps over(?)stretching it a bit:

• SiC Silicon carbide aka moissanite

And boron carbides like:

• B₄C Terraboron monocarbide

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• Metal carbides are NOT included here.
  So e.g. titanium carbide (TiC) is NOT counted as organic gemstone-like compound here.
  For these see: Simple metal containing carbides and nitrides

Why adding oxygen or sulfur only works for trace amounts

• Adding oxygen in high quanity leads to carbon dioxide CO₂ which is (as one should now) not stable as a covalently cross-linked solid
• Adding sulfur in huge quantity leads to carbon disulfide CS₂ wich is an (interesting) liquid in its thermodynamic stable form
• Nitrogen just wants to mind it's own business and wants to get back to its molecular di-nitrogen from with its strong tripple bond (usually a quite exoergic reaction)

Metastable solid state forms (not referring to being frozen) may be possible (especially at low temperatures) but activation energies are low making these compounds into dangerous high energy explosives.

Related

• Superclass: Metal free gemstone-like compounds

External links

• Inorganic compound – the exact definition is field dependents, so taking a bit of liberty here should be ok.