Melilite

Formula:  (Ca, Na)₂ (Mg, Al) (Si, Al)₂ O₇

Origin of name:  From Greek meli - honey because of colour

Crystal system:  Tetragonal

Crystal class:  -42m

Twinning:  On {001} or {100}

Unit cell: a = 7.79 Å, c = 5.02 Å

Colour:  yellow, brown

Diaphaneity: 

Luster:  Vitreous

Habit:  Equant to short prismatic

Hardness:  5 to 6

Specific gravity:  3.09

Cleavage:  2; {001} perfect, {110}

Tenacity: 

Streak: 

Synonyms/varieties:

Comments:  Member of the åkermanite-gehlenite series