CREATE TABLE table_79972 ("Rank" FLOAT, "Mine" TEXT, "County" TEXT, "Operator" TEXT, "Source of copper" TEXT, "2012 Cu Production  ( lbs ) " FLOAT)

What's the lowest ranking source of copper, copper ore, concentrated and leached?
SELECT MIN("Rank") FROM table_79972 WHERE "Source of copper" = 'copper ore, concentrated and leached'
SELECT MIN("Rank") FROM "table_79972" WHERE "Source of copper" = 'copper ore, concentrated and leached'