Deltalumite

A polymorph of leukosapphire.
This compound/material/gemstone is interesting because normally Al₂O₃ forms leukosapphire (corundum structure).

Al₂O₃ Deltalumite (δ form of corundum, polymorph of sapphire) – tetragonal – Mohs ?? (likely quite hard) – [1]

Its structural formula can be written as (Al_0.67◻_0.33)Al₂O₄, where ◻ is a vacancy.

Oxospinel type structure.

Papers

"Deltalumite, a new natural modification of alumina with spinel-type structure"

• Researchgate Jannuary 2019 [2]
• Researchgate December 2020 [3]
• (semanticscholar) << Images!

How to spell this? Delt-alumite? Delta-lumite? Delta-alumite?

Related

• Base materials with high potential
• Gemstone
• Leukosapphire

External links

• https://www.wikidata.org/wiki/Q27013457
• Paper including figures showing projections of the structure
  https://link.springer.com/article/10.1134/S1075701520070089