Clades:
Nesosilicates.
Chemical: (Ce,La,Nd,Y)2FeBe2Si2O10.
Crystal system: Monoclinic.
Color: black.
Lustre: vitreous.
Hardness: 6.5 to 7.
Specific gravity: 4.0 and 4.7.
MineralogyGadolinite is fairly rare and typically occurs as well-formed crystals.
It fractures in a conchoidal pattern and streaks grayish-green.
It can emit visible light when heated to relatively low temperatures, so is possible has pyrognomic properties, but the scientific consensus is that this is the product of thermoluminescence.