Polylithionite from the rare-metal deposits of the Blachford Lake alkaline complex, N.W.T., Canada

Extensive deposits of rare lithophile elements are located within albitized and greisenized peralkaline granite and syenite at Thor Lake, in the Blachford Lake complex, E of Yellowknife, Northwest Territories of Canada. Polylithionite is a major phase in several units of mineralized zones; its abundance amounts to tens of thousands of tons. The chemistry, physical properties and structural characteristics of two polylithionite samples from widely separated locations are almost identical, and are close to the typical properties of the end-member 1M polylithionite.