[yoo-ran-uh-nahyt, -rey-nuh-]
  1. a mineral, probably originally uranium dioxide, UO2, but altered by radioactive decay, and usually containing uranium trioxide, lead, radium, and helium, occurring in several varieties, including pitchblende: the most important ore of uranium.

Origin of uraninite

First recorded in 1875–80; uran(ium) + -in2 + -ite1
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for uraninite


  1. a blackish heavy radioactive mineral consisting of uranium oxide in cubic crystalline form together with radium, lead, helium, etc: occurs in coarse granite. Formula: UO 2

Word Origin for uraninite

C19: see uranium, -in, -ite 1
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012