1. A black or dark brown mineral containing uranium and thorium oxides, formerly used as a source of radium.
Usage: mineralogy; historical

Examples

• Cleveite was an important ore mineral in the early study of radioactivity.
• The discovery of cleveite deposits in Norway contributed to early uranium research.
• Scientists analyzed cleveite samples to extract radium in the late 19th century.
• Cleveite is now primarily of historical interest to mineralogists and nuclear historians.