Allanite

About Allanite

Allanite belongs to the silicate class in the epidote group / ree-bearing epidote and has the chemical formula (CaCe)(Al2Fe2+)(Si2O7)(SiO4)O(OH). It crystallizes in the monoclinic system and holds a steady position among silicate species.

Identification & care

Crystals commonly develop as prismatic to tabular crystals; also massive, disseminated; commonly metamict (amorphous from radiation damage). Its color is typically black to brownish-black, dark brown and rarely translucent greenish-brown in fresh material. The luster is vitreous, sub-metallic, resinous; pitchy when metamict, the streak is gray to grayish-brown, and specimens are typically opaque; rarely translucent. The cleavage is imperfect {001} and {100}. The fracture is conchoidal to subconchoidal; often metamict, which aids identification.

Collector context