|Transparency||Transparent to translucent|
|Comments||Not attached by acids|
In 1937, gemologists B.W. Anderson and C.J. Payne reported the existence of a zinc-rich type of gem spinel which is transitional between spinel and gahnite. The name gahnospinel was then suggested for this species, which ranges from pale to dark blue and green.
Optic character will serve to separate gahnospinel from sapphire, the gem with which it is most likely to be confused.
Gahnospinel may be polished and faceted in the same manner as spinel, with crown angles of 37° and pavilion angles of 42°.