The Lavender Pit copper mine at Bisbee was worked by open-pit mining from 1917 to 1974. At its maximum, the pit measured 4,000 feet wide from north to south, 5,000 feet long, and 850 feet deep. Large circular concrete structures remain from a concentrate thickener, which used a chemical flotation process to separate metal from rock in finely ground ore, after which the concentrate was shipped to a distant smelter for further processing. Near Highway 80 at the extreme left of the open pit are the remains of the crusher, which broke large chunks of ore into smaller rocks, and a conveyor belt then carried the crushed rock to the mill and concentrator on the hill beyond the pit. More than 300 different types of minerals are found in the hills around Bisbee, including rusty-red oxidized sulfide minerals, gray granite porphyry containing small amounts of copper, a thin yellow layer of breccia surrounding the granite, and purple or lavender limestone and conglomerate along the south and east sides of the pit that contain no copper and are considered waste rock. The pit was named not for its color but for Harrison Lavender, a former Phelps Dodge general manager of Western Operations. Nearly a century of production in Bisbee yielded some 8 billion pounds of copper, while worldwide copper consumption is now about 34 billion pounds each year.