Process for recovering alkali metal values from lepidolite

Claim 1

A PROCESS FOR RECOVERY OF LITHIUM VALUES FROM AN ORE CONTAINING LEPIDOLITE COMPRISING CALCINING A MIXTURE CONSISTING ESSENTIALLY OF FROM ABOUT TWO TO ABOUT FOUR PARTS OF AVAILABLE CALCIUM CARBONATE TO ONE OF LEPIODLITE AT A TEMPERATURE OF FROM ABOUT 800* TO ABOUT 100*C. FOR A TIME SUFFICIENT TO PROVIDE A ROASTED MATERIAL CONTAINING CALCIUM CARBONATE EQUIVALENT TO FROM ABOUT 4% TO ABOUT 8% CARBON DIOXIDE, QUENCHING THE ROASTED MATERIAL, GRINDING AND LEACHING THE QUENCHED MATERIAL TO FORM A SLURRY CONTAINING ALKALI METAL HYDROXIDE AND LITHIUM FLUORIDE IN SOLUTION, SEPARATING INERT SOLIDS FROM SAID SLURRY TO PROVIDE A SOLUTION, CONCENTRATING SAID SOLUTION TO PRECIPITATE LITHIUM HYDROXIDE MONOHYDRATE AND LITHIUM FLUORIDE, FILTERING THE RESULTING MIXTURE TO SEPARATE A SOLID MIXTURE OF SOLID LITHIUM HYDROXIDE MONOHYDRATE AND SOLID LITHIUM FLUORIDE, DISSOLVING THE SOLID LITHIUM HYDROXIDE MONOHYDRATE FROM THE SOLID MIXTURE AND FILTERING THE SO-FORMED SOLUTION TO SEPARATE UNDISSOLVED SOLID LITHIUM FLUORIDE FROM THE FILTRATE, AND CRYSTALLIZING A CROP OF REFINED LITHIUM HYDROXIDE MONOHYDRATE FROM THE LAST MENTIONED FILTRATE.