March 17, 2017
ASARCO Mineral Discovery Center
The Mission open-pit copper mine was at one time five separate mining
properties, but over the years, Asarco has combined them into one
integrated mining operation. The mine occupies around 20,000 acres of
private, State leased, and Indian land. There are over
600 employees working two shifts, 24 hours a day, seven days a week.
Each year the mine has the capacity to process about 260,000 tons of
copper concentrates which yields 132,700,000 pounds of copper and
1,234,000 ounces of silver. Annually, the Mission mine pays royalties
and taxes to the State of Arizona and royalties to the Tohono O’odham
There is some old equipment near the building housing the gift shop and a small museum. The large truck on the left was too small to be run economically. It was replaced by a truck much larger that cost about $5,000,000. They currently have 24 such trucks. The six tires on the trucks cost $50,000 each and last about 6 months before having to be replaced. At one time the old tires were recycled, however they had too many of them and the market dried up. Now the tires are dumped into a played out pit and covered up.
Structure from an old mine that is near the visitors center.
The different colored rocks from the tailings pile come from different layers in the mine pit. These pilings can be seen from I-19 for miles and the view from google earth show how large these mines are. They are nothing more than ground up rocks with the copper removed.
An 11-foot-diameter tire from a 240-ton haul truck provided a
great photo opportunity
The first stop on our tour was the open-pit viewpoint on the south
rim of the Mission Mine. The viewpoint was securely fenced for safety, and it has four binocular telescopes to provide a close-up view
of the trucks and shovels working in the mine.
The Mission Mine is a quarter-mile deep, two miles from north to
south, and a mile-and-three-quarters from east to west. About six times
the amount of earth moved to dig the Panama Canal has been mined here.
The haul trucks carry the ore out of the pit along a haulage
road with a slope of no more than about nine percent. They dump the ore
into a gyratory crusher which reduces the ore to eight inches or less —
about the size of soccer balls. The primary crusher may send the
crushed ore on to a secondary crusher or pile it directly onto the
coarse ore stockpile.
The South Mill
At the Mill, the copper ore is ground into a powder so the copper minerals can be separated by the froth flotation process.
There was more to the tour but my old memory isn't what it used to be, so you will have to take the tour yourself to hear it all.
I was chatting with the tour guide and asked if they backfilled the pits like they do with strip mining in Illinois where Gerry and I grew up. She said no and then asked where in Illinois we lived and when I said 50 miles south of Springfield she then asked what town. It was becoming apparent to me that she knew the area. When I said Gillespie, IL she said she went to middle school there, high school in Mt. Olive and Litchfield, IL What a small world we live in when a perfect stranger connects with you over where you lived.
BTW: She did a fine job on the tour and hopefully if you take it, she will be your guide.
That was our day, how was yours?