Uranpyrochlore (Ellsworthite) - MacDonald Mine, Monteagle Township, Hastings Highlands Municipality, Hastings County, Ontario, Canada

(Ca,U,Ce)₂(Nb,Ti,Ta)₂O₆(OH,F)                            

Uranpyrochlore from the MacDonald Mine, located in Ontario, Canada, is a rare and highly sought-after mineral within the pyrochlore supergroup. This mineral is characterized by its complex chemical composition, typically rich in uranium and niobium, often accompanied by smaller amounts of thorium, titanium, and rare earth elements. Its crystalline structure is cubic, forming isometric crystals that can range from microscopic grains to larger, more defined specimens. At the MacDonald Mine, uranpyrochlore occurs as an accessory mineral within pegmatites and carbonatites, often associated with other rare earth minerals, feldspars, and quartz. Its coloration varies depending on its uranium content, ranging from yellow to brownish hues, with a vitreous to submetallic luster.

The uranpyrochlore from this locality holds scientific and economic interest due to its significant uranium content, which is a key factor in its radioactivity. Its high uranium levels make it a valuable indicator of geochemical processes and mineralization in rare-earth-rich deposits. Specimens from the MacDonald Mine are especially prized by collectors and researchers for their well-formed crystals and historical relevance, as the mine played a notable role in Canada's mineral exploration history. Due to its radioactive nature, handling uranpyrochlore requires caution, and its study often involves detailed radiometric analysis to better understand its composition and the geological conditions of its formation.

Approx. specimen size: 40mm x 25mm x 20mm

Approx. activity using an SE International Ranger EXP: 16000 cpm

Specimen comes mounted in pictured membrane case.