I have what I am told is a seroquel, it is white, oblong and has only 259 printed on it?

Pill imprint 259 has been identified as Quetiapine fumarate 300 mg. (Generic for Seroquel)

Quetiapine is used in the treatment of bipolar disorder; schizoaffective disorder; borderline personality disorder; generalized anxiety disorder; schizophrenia (and more), and belongs to the drug class atypical antipsychotics.

Pill image: https://www.drugs.com/imprints/259-20674.html