Khmaralite

The mineral khmaralite is a beryllium bearing mineral of the sapphirine group with a chemical formula of (Mg,Al,Fe)16[(Al,Si,Be)12O36]O40. It is most associated with sillimanite, surinamite, musgravite, garnet, and biotite. The known color is a dark greenish blue or a dark green, with a colorless streak. It is transparent with a vitreous luster with no cleavage and a Moh's hardness of 7. It is brittle with an uneven fracture. The calculated density is 3.61 g/cm3. Khmaralite is closely related to sapphirine with a difference in the tetrahedral sequence chain. The tetrahedral sequence chain in sapphirine (Al-Si-Al) is replaced by the sequence Si-Be-Si in khmaralite. Si is replaced by Be on two sites, and Al is replaced by Si on four adjacent sites. This creates an indirect replacement of Al by Be.