CHEMISTRY - (Ca,Ce)2 (Al, Fe,2 Fe3)3 (SiO4) (SiO7) O (OH)
CRYSTALLOGRAPHY - Monoclinic
CRYSTAL GROWTH AND HABITS - Crystals are commonly tabular, prismatic to acicular. It can also be massive or granular.
COLOR AND OTHER OPTICAL PROPERTIES - Commonly brown to black. Translucent to opaque.
HARDNESS - 5.5 - 6
SPECIFIC GRAVITY - 3.5 - 4.2
LUSTER - Vitreous to resinous or sub metallic
STREAK - Gray
BREAKABILITY - Imperfect cleavage on {001} and poor on {100} and {110} with an uneven to conchoidal fracture. Allanite is brittle.
OCCURRENCE - Allanite is an accessory mineral in granites and granitic pegmatites and in syenites. It is also occasionally found in schists and gneisses and as grains in sedimentary deposits.
ASSOCIATED MINERALS - Muscovite, Epidote, Fluorite
NAME - Named after the Scottish mineralogist Thomas Allan who discovered the species.