Minerals identify

Know how to recognize them



Melilite refers to a mineral of the melilite group of several endmembers, the most important of which are gehlenite and åkermanite. A generalized formula for common melilite is (Ca 2+)[(Al. Discovered in 1793 near Rome, it has a yellowish, greenish-brown color. The name derives from the Greek words meli (μέλι) "honey" and lithos (λίθους) "stone".

Minerals of the melilite group are sorosilicates. They have the same basic structure, of general formula A2B(T2O7). The melilite structure consist of pairs of fused TO4, where T may be Si, Al, B, in bow-tie form. Sharing one corner, the formula of the pair is T2O7. These bow-ties are linked together into sheets by the B cations. The sheets are held together by the A cations, most commonly calcium. Aluminium may sit on either the T or the B site.

Minerals with the melilite structure may show a cleavage parallel to the (001) crystallographic directions and may show weaker cleavage perpendicular to this, in the {110} directions. Melilite is tetragonal.

The important endmembers of common melilite are åkermanite Ca2Mg(Si2O7) and gehlenite Ca2Al and sodium.

Some other compositions with the melilite structure include: alumoåkermanite Ca2B Ca2Zn, andremeyerite. Some structures formed by replacing one oxygen (Ca,Na)2(Be,Al) (Ca,Na)2(Be,Al) (Ca,Na)2(Be,Al)

New members of this mineral group were artificially grown and became intensively studied due to their multiferroic property, i. e. they simultaneously show ferroelectric and magnetic ordering at low temperatures. This gives rise to peculiar optical properties, for example Ba2Co(Ge2O7) shows giant directional dichroism (different absorption for counter-propagating light beams) and hosts magnetically switchable chirality


Color of mineral


Mohs scale ( mineral hardness )


The streak


Density ( specific gravity )


Luster ( interacts light )


Crystal ( diaphaneity )