1. A black or dark brown mineral containing rare earth elements, especially yttrium and gadolinium, used as a source of rare earth metals.
Usage: mineralogy; technical

Examples

• Gadolinite is an important ore mineral for extracting rare earth elements.
• The geologist identified gadolinite in the rock sample under the microscope.
• Gadolinite deposits are found in granitic pegmatites around the world.
• Mining companies seek gadolinite as a source of gadolinium and yttrium.
• The dark crystals of gadolinite contain valuable rare earth metals.