Gadolinium (Gd) is contained in the following rare earth mineral:
Allanite
Fergusonite
Obruchevite
Gadolinium has particular properties that make it especially suited for important functions, such as shielding in nuclear reactors and neutron radiography. It can target tumors in neuron therapy and can enhance magnetic resonance imaging (MRI), assisting in both the treatment and diagnosis of cancer. X-rays and bone density tests can also use gadolinium, making this rare earth element a major contributor to modern health care solutions.
References
https://en.wikipedia.org
https://en.wikipedia.org/wiki/Gadolinium