# Minorca Mine

# ArcelorMittal Profile

ArcelorMittal is the world’s number one steel company, with 310,000 employees in more than 60 countries. It has led the consolidation of the world steel industry and today ranks as the only truly global steelmaker.

ArcelorMittal is the leader in all major global markets, including automotive, construction, household appliances and packaging. The Group leads in Research and Development and technology, holds sizeable captive supplies of raw materials and operates extensive distribution networks.

Its industrial presence in Europe, Asia, Africa and America gives the Group exposure to all the key steel markets. It enjoys a leadership position in technically advanced products. It benefits from a high level of vertical integration – from iron ore mining at one end of the value chain to steel service centers and distribution at the other.

ArcelorMittal’s strategy is to build a sustainable and stable business, creating value through the cycle, through scale and diversification. At the same time, the company is focused on setting the standard in areas such as health and safety, quality, delivery and customer satisfaction. ArcelorMittal remains engaged with the communities in which it operates and steadfast in its commitment to good environmental practice. 

# Core Values

Transforming tomorrow: Our Philosophy, Our Values
We know that our position in the steel industry brings unique responsibilities. We are committed to setting globally recognized standards with the needs of future generations in mind.

Our goal is to provide the leadership that will transform tomorrow’s steel industry. We have a clear vision of the future, underpinned by a consistent set of values.



### Sustainability We are guiding the evolution of steel to secure the best future for the industry and for generations to come.

Our commitment to the world around us extends beyond the bottom line, to include the people in whom we invest, the communities we support and the world in which we operate. This long-term approach is central to our business philosophy.



### Quality We look beyond today to envision the steel of tomorrow.

Because quality outcomes depend on quality people, we seek to attract and nurture the best people to deliver superior solutions to our customers.



### Leadership
We are visionary thinkers, creating opportunities every day.

This entrepreneurial spirit brought us to the forefront of the steel industry. Now, we are moving beyond what the world expects of steel.

For more information, please visit www.arcelormittal.com

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### Geology Minnesota’s future as the iron-ore capital of North America was assured more than 2 billion years ago. Then, a vast shallow sea covered much of what is now the Mesabi Iron Range. As time passed, material rich in iron and silica was deposited on the floor of this sea in thin, alternating layers. Because the water of this vast inland ocean was low in free-oxygen content, the material also was low in oxygen, helping to prevent decomposition. This period of geologic formation ended with the return of more common forms of sedimentation, such as mud, clay and sand. As the centuries passed, the weight and heat generated by this accumulation of material converted the iron and silica into taconite, a hard flinty rock containing about 22 percent magnetic iron. The eastern portion of the Mesabi Range, where Minorca is located, also benefited from the intrusion of hot, molten rock known as the Duluth Gabbro. At about the same time, the iron-rich rock strata was tilted between 3 degrees and 12 degrees to the southeast.

The next stage of geologic formation occurred as the overlying rocks were slowly worn away, exposing the iron-rich strata to oxygen and water. These entered the formation along porous zones and fractures, reacting with the oxygen-poor minerals. As a result, the minerals oxidized to form hematite, or “red ore,” while the silica was washed away. The result was rich, red-ore bodies surrounded by oxidized (nonmagnetic) and unoxidized (magnetic) taconite.

Most of the red ore in the Mesabi Range was exhausted by the military buildup for World War II. New processes were developed to mine and extract the remaining iron-bearing material from the lower-grade taconite ore. As these sources of iron are depleted, technology may be developed to use the remaining nonmagnetic ore.

Typical Laurentian Mine Cross Section 

# Steel is the fundamental raw material of the 21st century, widely used in the manufacture of products for a variety of markets such as automotive, appliance, construction, office equipment, packaging and others.

ArcelorMittal USA is the largest steel manufacturer in North America. ArcelorMittal Minorca, near Virginia, Minn., is one of the company’s leading sources of iron ore – a major raw material required in the manufacture of steel. Each year, Minorca produces about 2.8 million tons of fluxed iron-bearing pellets, and mines about 18 million tons of ore, rock and waste material, called overburden. The pellets are then shipped to ArcelorMittal Indiana Harbor, North America’s largest integrated steelmaking complex located in East Chicago, Ind., about 20 minutes southeast of Chicago. There, the pellets are charged into Indiana Harbor’s massive No. 7 Blast Furnace – the largest iron producer in the Western Hemisphere, capable of producing more than 12,500 tons of molten iron a day. Minorca supplies about 50 percent of No. 7 Blast Furnace’s pelletized iron requirements.

Blast hole survey. 1800

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1200

1000

800

600 Burden

Lean Tac

UC-3 Ore

Waste Rock

LC-5B Ore LC-5A Ore

LC-4 Ore UC-2 Ore UC-1 Ore

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### History In 1780, nearly 150 years after the first French explorers visited northern Minnesota, the first recorded discovery of the iron-rich rock strata of the Lake Superior District was made on the Gunflint Range. Almost 90 years later, in 1886, iron-bearing rock – although not ore in the commercial sense – was discovered at both ends of the Mesabi Range. Mineable ore was first discovered four years later, in 1890, about five miles west of what is now Minorca Mine.

This discovery triggered rapid exploration and development of red ore mining capability. By 1900, the main outline of the Mesabi Iron Range was basically defined. As the richest portions of these direct shipping red ore deposits were exhausted, tons of leaner mixtures were encountered. This ore could be upgraded by simple washing and screening techniques. These methods were first employed on a large scale in 1910. As reserves of natural high-grade ores diminished, mining operations increasingly turned to such procedures until nearly all of the remaining red ores were mined and upgraded.

Early on, it was recognized that the hard, lean, dark-colored rock that surrounded the brightly colored red-ore bodies was highly magnetic. It also was discovered that the eastern 20 miles or so of the Mesabi Iron Range was composed of this same hard, flinty rock, called magnetic taconite. The first effort to upgrade these ores on a commercial scale was made in 1918. However, due to the high cost of mining, crushing and grinding the extremely hard rock, this small-scale operation ceased in 1924. The modern age of magnetic taconite mining and processing had to await the development of new techniques, such as jet-piercing and pelletizing, before it could resume in the early 1950s.



### Minorca Mine Development Shortly after World War II, Inland Steel Co. acquired half ownership of the Pacific Isle Mining Co., which held natural-ore mining leases on property encompassing the Minorca Mine. The company purchased the remaining interest in Pacific Isle in 1960, and began exploratory drilling for taconite in 1962. The natural-ore leases held by Pacific Isle were amended to include taconite, and additional mining properties were leased. Land on which to build the plant and auxiliary facilities was acquired from the U.S. Forest Service, state, county, and other corporate and private land owners.

A study then was made to determine if sufficient water was available for operation of a taconite plant. In 1973, preliminary engineering and cost/benefit studies were made. Based on the results of these studies, the company’s board of directors authorized the development of the Minorca Mine Taconite Project in 1974. The first shipment of taconite pellets was made in June 1977. Minorca Mine was originally owned by Inland Steel Mining Co., which was formed in 1974 as a wholly-owned subsidiary of Inland Steel Co., an operating subsidiary of Chicago-based Inland Steel Industries Inc.

In 1993, the company opened up a new ore body called the Laurentian Mine near Gilbert, Minn., about six miles from its production facilities. In 1998, Inland Steel and Minorca Mine were purchased by Ispat International and renamed Ispat Inland Inc. In 2006, the company became Mittal Steel. Finally in 2007, the merger between Mittal Steel with Arcelor formed the largest steel company in the world – ArcelorMittal. The Minorca operation was then renamed ArcelorMittal Minorca.

In 2007, ArcelorMittal began mining the East Reserve between McKinley and Biwabik, Minn.

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### Minorca Mine Operation Overview

1. Taconite ore is drilled, blasted and trucked to the plant. Overburden and rock are trucked to stockpiles.



### 2. Taconite is crushed to football-sized chunks in the primary crusher.



### 3. Ore is moved by conveyor to an intermediate stockpile.



### 4. Ore is crushed to gravel-size during second-and-third-stage crushing.



### 5. Ore is moved by conveyor to the fine ore stockpile. 

### 6. Ore is ground to face-powder size in rod and ball mills. Iron-bearing particles are separated from the ore magnetically and chemically. Finely-ground fluxstone is mixed with the concentrate.



### 7. Fine tailings are partially dewatered in the tailings thickener and pumped to an enclosed basin. Coarse tailings are trucked to a stockpile.



### 8. Fluxstone (55 percent dolomite and 45 percent limestone) is crushed and ground in the fluxstone grinding plant. 

### 9. A clay binding agent is added to the taconite concentrate and rolled into marble-sized pellets.



### 10. Pellets are heat-hardened at 2,450o F in a gas-fired furnace.



### 11. Finished pellets are stockpiled prior to train shipment to Two Harbors, Minn.; then moved by boat to Indiana Harbor, East Chicago, Ind.



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ArcelorMittal Minorca Mine | 5Fluxed pellets from Minorca Mine travel three days across the Great Lakes, where they are stockpiled at ArcelorMittal Indiana Harbor.

Photo: Mr. François Trahan, 2006

Iron ore pellets and other raw materials are used in blast furnaces, such as ArcelorMittal Indiana Harbor’s No. 7 Furnace, to produce liquid iron. BALL MILL BIN TAILS

TANK

SCREEN

HL HL1,2 HL3,4

RECLAIM GRIZZLY HL OU2,3 FEEDER STAMLER FCR1

BIN HL MD-2BINSPLITTER CRUDE ORE

SCREEN CRUSHER TERTIARY CRUSHER SECONDARY

52CV02,3,4,5,6,7,8,951CV09,52CV01 44CV01 43CV01 C-3

FINE SCREEN

TANK STORAGE SLURRY FLUXSTONE BALL MILL CRUSHER

BIN FLUX FLUXSTONE UNLOADING

SUMP FMS

FLOT PLANT

TANK SLURYCONCFLUXED

TANK SLURRYCONCACID THICKENER CONCENTRATE FINISHERS FINE SCREENS

HYDRO-SEPARATOR

DESLIMING CYCLONE

TO TAILINGS BASIN TAILS THICKENER ROUGHER SPIRAL CLASSIFIER 62CV-01

FCS-1 FC 1,2,3,4,5,6,7

FILTERS

BALLING DISC BIN STORAGE CAKE FILTER BIN BENTONITE BIN PERIDUR REPULPER
GP 1,2,3,4

MACHINE INDURATING

PELLET LOAD-OUT P-1,P-2

MD-1 P-3 STOCKPILE MD-2 COBBER ROD MILL PRIMARY CRUSHER

PELLET STOCKPILE FILTER CAKE STOCKPILE BLENDING PILE FINE ORE SURGE PILE COARSE

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### Drilling and Blasting
A 16-inch rotary drill makes between 100 and 200 holes for each blast site in a grid 26 feet by 30 feet. Each hole is drilled into the rock strata to a depth of 35-50 feet. Next, about 3,000 pounds of ANFO, an explosive mixture of ammonium nitrate and fuel oil, is bulk loaded into each hole and covered with a 16- foot plug of crushed rock called “stemming.”

Each blast carries the explosive force of more than 250,000 pounds of dynamite and dislodges between 200,000 and 300,000 tons of rock. The blast is triggered sequentially using 25-millisecond, nonelectric delay units between each hole, sending an explosive shock wave through the rock that fragments the taconite into pieces ranging in sizes from just inches to boulders several feet in diameter. Rock type and hardness determine the blast design, but about one pound of explosive is needed to break each ton of taconite ore. The broken crude ore, which contains about 22 percent magnetic iron, is excavated by giant loaders equipped with 19-cubic-yard buckets and then dumped into 195-ton or 240-ton haul trucks, and delivered to the plant for processing. 

### Stripping
Before iron can begin its journey to liquid steel, it must be mined as ore from the ground. To begin, earth and waste rock covering the ore must be removed and placed in stockpiles. For every ton of ore mined, about one ton of overburden and waste rock must be removed.

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### Fine Crushing
A conveyor beneath the coarse ore stockpile moves the ore to the fine crushing plant, where it is reduced to less than 5/8 inch in second-and-third-stage crushers. Ore crushed to the desired size is continuously moved by conveyor to the fine ore stockpile. A traveling conveyor deposits ore on the pile and ensures the ore is blended for increased quality and uniform plant feedstock.



### Rod Mills Conveyors beneath the fire ore stockpile move the ore to the concentrator building, where it enters one of three identical processing lines. First, the ore is fed by conveyor into rod mills, where it is mixed with water to form a slurry, for ease of transport through the remainder of the grinding process. Inside the rod mill, 200 tons of hardened steel grinding rods, each 19.5 feet long, four inches in diameter and weighing 800 pounds, tumble over the slurry, reducing the size of the ore particles to about the consistency of sand. 

### Coarse Crushing
The 54-inch diameter primary crusher reduces boulder-sized pieces of taconite to about the size of a football. As crude ore is dumped into the top, gravity pulls the rocks downward, where the crusher breaks them into even smaller pieces, operating like a huge inverted mortar with a circular motion pestle. A conveyor belt moves ore from beneath the crusher to a 70,000-ton coarse ore stockpile. The process takes about five minutes.

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### Magnetic Separation Ore discharged from the rod mill is fed into rotating magnetic separator drums called cobbers, which extract the iron-bearing material from the surrounding silica and rock. This waste silica and rock, called tailings, flows by gravity to a classifier that separates the tailings by size. Coarse tailings are trucked to stockpiles where they later will be used for roads or other construction applications. Fine tailings are sent to a tailings thickener for partial dewatering and then pumped to a reservoir called a tailings basin, where tailings are allowed to settle to the bottom and the clarified water is pumped back to the plant.



### Ball Mills
Following magnetic separation, the ore moves to the ball mills where 350 tons of rotating steel balls, each 1.5 inches in diameter, reduces the ore to about the consistency of face powder. The ore is then passed through a second series of magnetic separators called roughers. The rougher concentrate is size-classified by cyclone separators. The cyclone overflow moves to hydroseparators, where the ultra-fine material is rinsed out of the concentrate. Concentrate from the hydroseparators is then pumped to vibrating screens, which again size-classify the material to ensure the correct particle size and consistency. The oversize from these screens is fed back into the ball mill for further reduction. The undersized material is fed to the final series of magnetic separators called finishers.



### Flotation Separation The slurry concentrate moves to the final stage of processing: flotation separation. Through the use of chemicals, air and mechanical agitation, bubbles are formed in each of eight 1,000-cubic-foot flotation cells. The fine particles of silica attach to the bubbles and are removed from the concentration process. Flotation concentrate is pumped back to the concentrate thickeners and the silica from the cells is subjected to additional grinding and flotation. This recovers iron trapped in the froth, which otherwise might be lost in the process. 

### Thickeners

The flotation concentrate is fed to two concentrate thickeners where partial dewatering of the concentrate occurs. At each stage of the concentration process, waste material is pumped to a tailings thickener and partially dewatered. Water from the process – about 70,000 gallons a minute – is cleaned and returned to the manufacturing process. Tailings are pumped to an enclosed basin, where they settle to the bottom, and the clarified water is pumped back to the plant and reused.

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### Flux Grinding Plant
In 1987, Minorca Mine introduced the first fluxed pellet on the Mesabi Iron Range. Fluxed pellets improve blast furnace productivity, make higher-quality iron, and reduce energy and maintenance costs. Limestone and dolomite, called fluxstone, arrive at Minorca in railroad cars. The fluxstone is then crushed in a slurry much like taconite and ground to about the consistency of face powder in the flux grinding plant. The finely-ground slurry is then pumped into a 40-foot diameter slurry holding tank in the concentrator building, where it is mixed with the iron-rich concentrate at a specified rate and ratio.



### Disc Filters

Indurating Furnace The fluxed taconite concentrate now undergoes dewatering through a series of disc filters. Water is removed from theconcentrate by vacuum on a series of clothcovered discs. What remains on the disc is filter cake containing about 9 percent water and more than 62 percent magnetic iron.

The green, unfired pellets are conveyed to a 13-foot-wide traveling grate to begin their 250-foot trip through the indurating furnace. Inside, the balls are dried andheat-hardened at 2,450o F in six, carefullycontrolled heating and cooling zones. 

### Balling Discs

The dewatered filter cake is mixed with bentonite clay, a kind of glue that will hold the pellet together through the baking process. The mixture is then rolled into marble-sized balls on rotating 19-foot diameter discs.

COOLING AIR FAN DRYING ZONE PREHEAT BURNERS

UPDRAFT

UPDRAFT DRYING FAN HOOD EXHAUST FAN

FIRING FIRING ZONE

WINDBOX RECOUP FAN WINDBOX EXHAUST FAN

DRYING ZONE DOWNDRAFT ZONE COOLING COMBUSTION CHAMBERS

AFTER SECOND COOLING

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### Shipment
The finished pellets are transferred to a loading pocket for shipment 75 miles to Two Harbors aboard 116-car unit trains. At Two Harbors, the pellets are loaded into Great Lakes ore freighters (the size of three football fields), which carry them to ArcelorMittal Indiana Harbor, more than 450 miles away. The three-day journey takes the pellets across Lake Superior, through the Soo Locks, down the St. Mary’s River, into Lake Huron, through the straits of Mackinac and into Lake Michigan.



### Process Control
All process equipment is monitored from a central, computerized control room. In 2007, a Distributed Control System (DCS) was installed to monitor stack emissions throughout the processing plant. It is also being used to record plant operating data in real-time and serves as a helpful tool in optimizing plant performance.



### Reclamation New pit slopes and filled tailings cells are planted with native grasses and trees each year to prevent soil erosion and control fugitive dust.



### Quality Control
Technicians at Minorca constantly monitor, test and analyze oresamples to ensure the highestquality fluxed pellets.

An X-Ray Fluorescent Unit is used to measure pellet quality.

ArcelorMittal Minorca Mine | 11ArcelorMittal Minorca Iron Mining 5950 Old U.S. Highway 53 Virginia, MN 55792 USA

T +1 218 749 5910 www.arcelormittal.com