Högbomite

Formula:  (Mg,Fe)₂(Al,Ti)₅O₁₀

Origin of name:  For A. Högbom, Swedish geologist

Crystal system:  Hexagonal

Crystal class:  6mm

Twinning: 

Unit cell: 

Colour:  Black

Diaphaneity:  Opaque

Luster:  Metallic adamantine

Habit:  Crystals thin to thick tabular, minute embedded grains, polytype 24R as 0.01 - 0.1 μm octahedral grains

Hardness:  6.5

Specific gravity:  3.93

Cleavage:  1; {0001} imperfect

Tenacity: 

Streak:  Grey

Synonyms/varieties:

Comments:  Data are for Högbomite-4H; there are also -5H, -6H, 8H, -15H, 15R and -18R polytypes; weakly magnetic