Part 6: ASARCO Mission Mine Tour

20131203

Navigation Links
 Trip Home Page     

 


The Trip

I had not been to the open pit copper mines south of Tucson in perhaps 40 years.  Back then, since my Dad had many contracts with the mines, we got special tours into "forbidden" place.  These days, it is all about "visitor control", shuttle buses and spin control.  But, spin notwithstanding, it proved to be an interesting tour.

ASARCO was purchased by Groupo Mexico many years back.  Under Groupo's management, some "streamlining" was done, but the company is profitable.  Their properties include Mission Mines, Silver Bell, Ray Mines as well as properties within Mexico.

The Photos

The photos below are what we saw.

Next to the visitor's center, there were a number of antique pieces of mining equipment.  This is a steam engine used to run a water pump.

The outside grounds were nicely landscaped and included this multiple golden barrel cactus.

The growth pads of the barrel cactus was filled with intricate structures.

This is a tooth from the bucket of one of the production shovels.  These wear out and must be replaced every few weeks.


This is a steam-powered hoist.

This is an actual hoist head frame that was moved to the visitor's center site.

Another steam-powered water pump.

This is a small shovel bucket.  The current buckets are 6 times bigger.

This is a very early model gas or kerosene-powered internal combustion motor.  The item on the top is an open radiator tank.  On the ground to the left is a drill bit.

This is a bucket used in one of their smelter operations at another facility. 

This is a 16 cylinder, 4000 cubic inch, 2700 hp diesel motor that puts out 8000 ft-lbs of torque and weighs 15,000 pounds.

Electric motors made rapid inroads into the mining industry.  They were much more efficient and maintainable than steam engines.  The sled above is a water pump driven by an electric motor.

A much slusher bucket and winch which is used in underground mines.

This is a 310 ton Terex haul truck that can carry 160 tons of ore.  Photos below show the current generation of trucks.

I can only imagine the effort required to change a tire.

I am surprised that the truck was not sold as scrap.  The tires are on the order of $80K each when new.

We piled into the shuttle bus for the tour and got a view of the tailings pond in the distance (the white area).  The tailings are powdered rock and are pumped with water to the pond where the water is reclaimed.

Soon we came upon one of the current generation Komatsu trucks.  This one was chugging up the grade from the pit carrying overburden for dumping on the rim.  These trucks cost about $5M each and are diesel electric and are run 24/7 until a maintenance cycle is required.

The grade up to the dump is steep and the trucks can only do about 6 mph when fully loaded.

The first stop on the tour was the pit overlook.  In mining since the late 1950s, they have moved 5-6 Panama Canal's worth of material.  A matrix of drill holes are being dug to allow emplacement of explosive slurry.  These holes can be seen to the left of the drilling rig in the center of the photo.  Once the matrix is completed, the holes will be filled with explosive slurry and primers and the whole shelf will be dislodged and then removed.  Depending on the copper content of the material, it will either be loaded into trucks and hauled to the dump site or to the crusher for ore extraction.  The steps on the left represent the final slope of the pit.  All material not conforming to that slope will be dispositioned to either the dump or the crusher over time.

This bucket shovel is removing overburden for transport to the dump site.  The pond at the top of the photo is at the local water table.  The shovels are electrically driven with 4160 volt three-phase lines.

A drilling rig is preparing blasting holes for slurry.  Meanwhile, haul trucks are taking ore to the crusher.

This shelf has already been blasted into rubble.  The rubble is being loaded into the haul trucks.  Empty trucks are always available to allow 100% duty cycle on the shovel.  The power cable for the shovel is visible crossing the light-colored rock.

5-6 buckets are required to fill a truck.

The haul trucks dwarf conventional vehicles.

This pit is massive, but nowhere near the biggest open pit copper operation.  That honor, I believe, goes to the mine at Silver City, NM.  Santa Catalina Mountains and their 9800' peak are visible on the far horizon.

These trucks get going over 30 mph when empty on the downhill run.

The steep grades up to the dump wall slow the trucks to 6 mph when fully loaded.

One of the settling ponds where copper concentrate is separated from the processing fluids.

Depending on the ore recovery schedule and what is being removed from the pit, extra crushed ore can be stored to provide feed material when pockets of low concentration ore is encountered in the pit.  The partially processed ore can later be added to the feedstock for the ball mills.

When the partially processed material is re-introduced to the feedstock, the material is passed through a set of magnets to remove any steel grinding balls that may have escaped into the ore.  This is to prevent damage to the crushing machine.

The ball mills use 16 lb steel shot to crush the ore into powder.  As the mill turns, the balls fall onto the ore and perform the crushing.  There are a set of these mills running 24/7.

The powdered ore is mixed with water and a set of chemicals to neutralize acids from the minerals and float the copper to the top of these tanks.  Scrapers push the concentrate into troughs where it is washed out into settling ponds for recovery.

At the completion of the tour, we returned to the Visitor's Center to see some of the displays.  On the exit from the facility, we spotted this awesome christate sahauro near the road.

Normal sahauros have a circular growth cap.  This christate has a growth line.  Note the light colored line at the crest of the cactus.

From the mine, we headed south to Tubac to see the presidio.  Most of the exhibits were dimly lit, but still interesting.  This is a hand made grinding wheel used for producing flour.

This is the way that the indians did it: a metate and mano.

Another hand-made grinding wheel, this one a bit more sophisticated.

To the east of Tubac, the Multi-mirror telescope was visible on the peak of Mt. Hopkins.

An old wagon at the Tubac museum.

The mine tour was well worth the time and effort.  Mission Mine is a truly impressive operation and will continue that way for about 17 more years.  At that time, the ore body will be depleted.

Next:  the Tucson Botanical Gardens.

Navigation Links
Previous Adventure
Top of this Page
  Next Adventure
Trip Home Page  
Bill Caid's Home Page

Photos and Text Copyright Bill Caid 2013, all rights reserved.
For your enjoyment only, not for commercial use.