Iron is the third most abundant element in the Earth's crust. It is rarely found in its native form and usually exists in minerals as oxides and carbonates. The main iron ore minerals are magnetite, hematite, goethite, limonite, and siderite. India has significant iron ore reserves, estimated at around 29 billion tonnes. The major iron ore producing states are Odisha, Jharkhand, Chhattisgarh, Karnataka, Goa and Tamil Nadu. India produced around 56 million tonnes of iron ore in 1990-91, of which 57% was exported. The main use of iron ore is in the production of iron and steel, which have applications in infrastructure

1. ❖ Introduction
Iron is the most vital metal in human use. It constitutes 5.05% of the crust material and holds third position
in abundance after silicon and aluminium. It is rarely found in native condition except in meteorites and some
eruptive rocks. It enters into large number of rocks forming silicates and is widely available as oxides. The mineral
containing iron must be mineable at profit in order to be called an 'iron-ore.' The total world production of iron-ore
in 1990 was about 1,008 million tonnes (Economic Geology - Umeshwar Prasad) to which India's contribution was
about 55.5 million tonnes (contributing 5.5%) with 6th position in the world production.
Boiling Point: 5182°F (2862°C) Atomic Symbol: Fe
Melting Point: 2800°F (1538°C) Atomic Number: 26
❖ Mineralogy
Rich / chief ores are better than poor ores. What makes an ore rich? In the first place, the relative amount of iron
it contains. I will give that number in percent (%). One kilogram of magnetite, for example, contains 0.724 kg of
iron. If you get about 700 g of iron for every kilogram of magnetite ore you put into your smelter, you have a smelting
efficiency of almost 100 %. That is far from the reality of ancient smelting, however.
The chief ores of iron are its oxides and carbonates, the important of them are named below in the Table
Minerals Chem. Composition Iron (Fe %) Remarks
Oxides
Magnetite Fe3O4 72.4 % Blue black or brown black color and streak, sp.gr. 5.2
Hematite Fe2O3 69.9 % Steel grey to red color, streak cherry-red, sp.gr 5.2
Turgite 2Fe2O3.H2O 66.1 % Brown to red color, sp.gr. 4.2-4.7
Goethite FeO(OH) 62.58 % Brown to yellow, sp.gr 3.3-4.3
Lemonite FeO(OH) · n(H2O) 52 %
Carbonate
Siderite FeCO3 48 % Ash gery to brown streak, apgr. 3.69
1. Magnetite; Fe3O4 (Lodestone) Magnetite gets its name because it has the (rare) property of being magnetic.
More to the point, magnetism got its name because there was magnetite, possibly named after the place it
was first found, for example ""Magnesia" in present day Turkey. Magnetite melts at 1535° C (2795 °F) and
has a density around 5.2 g/cm3. The German name "Hammerschlag" ("hammer blow") refers to the stuff
coming off your hot iron when you beat it with your hammer. It's either iron oxide that has formed on your
iron, or iron particles spritzing off that immediately oxidize in air. In either case the stuff is mostly magnetite.
Magnetite is the "richest" iron ore, it contains a bit more iron than haematite. It is rather common and
found in large deposits. It may also be a part of the sand of "black beaches". The English name "lodestone",
from '"leading stone" refers to the magnetic properties of magnetite. It is one of only two natural materials
that can be permanently magnetized and thus are permanent magnets. In a compass, it shows the way.
2. Haematite or Hematite; Fe2O3 (Red Iron Ore) Haematite is the most common iron oxide. It melts at 1565°
C (2849 °F) and has a density around 5.2 g/cm3. The word "haematite" contains the Greek word "haima"
for blood. You know this from words like "haematoma" = localized collection of blood outside the blood
vessels or "haematologists" = (expensive) people who deal with bloody things. The reference to blood
simply acknowledges that the stuff is red. Blood is red because its "working" molecule haemoglobin contains
4 iron atoms.
Humankind used haematite because it supplies the color to ochre, some (powdered) clay colored yellowish
/ reddish by large amounts of incorporated haematite. Powdered ochre was used quite early - more than
100000 years ago - for painting things red, reddish or yellowish
3. Goethite FeO(OH) (Brown Iron Ore, Brown Ironstone). Goethite was named in honor of Johann Wolfgang
von Goethe (1749 - 1832), Germany's most famous writer. Goethe was also a "naturalist" and dabbled in
science, including mineralogy. He also was a politician, e.g. "Minister of mining" in Weimar. Goethite
transforms to haematite before it melts, It has a densiy of 4.3 g/cm3. Goethite is related to limonite and bog
iron. Goethite is no longer important in iron making. Its importance in older times is unclear because it was
not distinguished from siderite or bog ore. Goethite forms by "weathering" of more primary iron ores like
magnetite or pyrite, involving a change from Fe(II) compounds to the more stable Fe(III) form. It thus is
often found in the "gossan" (Eisenhut = iron hat) of iron ore deposits. Goethite then can be "pseudomorph",
meaning it keeps the shape of the iron compound it formed from. It thus may appear in shapes (including
nice "crystals") that do not express its own structure.
GL-Apr-2018 Last Update Aug-19 Economic Geology
Q U A R T Z Nikhil V. Sherekar
Iron

2. 4. Limonite FeO(OH) · n(H2O) (Brown hematite, brown iron ore (also used for Goethite); lemon rock,
yellow iron ore (if its orange / yellow). Because it is easy to find iron minerals in nature, often bright
orange, that are not magnetite, haematite, goethite and so on, but "somehow" iron hydroxides. The tendency
then is to name that stuff, and the name that stuck is limonite, after the Greek "leimon" = meadow. This
alludes to its appearance in "bog iron", found in meadows and marshes.
Limonite is some mixture of iron oxides and hydroxides, including goethite that one could also write as
Fe2O3.H2O, i.e. as haematite with crystallization water and, e.g., lepidocrocite (also called esmeraldite or
hydrohematite), jarosite (a pottassium-iron sulfate), haematite, maghemite (a kind of Fe(II)-deficient
magnetite), hisingerite (a "watery" iron(III) silicate), pitticite (a "watery" iron-arsenic sulfate / oxide), and
God knows what else. It is typically not recognizably crystalline but amorphous or simply "messy". You
might also call limonite "natural rust". Limonite, like goethite, usually forms from the weathering of more
primary iron ores like hematite or magnetite, but also from the oxidation and hydration of iron-rich sulfide
minerals and more complex stuff like olivine (iron plus some other metal silicate; extremely common in the
earth's crust but not stable close to the surface).
5. Siderite FeCO3 (chalybite, iron carbonate). Siderite is a well-liked ore because it is relatively easy to
smelt, if not as rich as some others. It can be reduced in two simple steps. First, just by getting hot, the
carbonate breaks down into FeO and carbon dioxide (FeCO3 Þ FeO + CO2). With hot carbon monoxide,
metallic iron is produced (FeO + CO => Fe + CO2). That is considerably simpler chemistry than what needs
to be going on for the other ores, and that is one of the reasons why siderite is easy to smelt. Siderite got its
name by some unimaginative Frenchman who just used the Greek "sideros" = iron for naming a mineral that
had been know and used for millennia under other names. It is a simple carbonate and quite ubiquitous. One
particular well-know huge deposit (400 Mio tons) is in present-day Austria. It has been mined in Roman
times and before and it is mined today. 250 Mio tons have been removed so far.
❖ Origin
Almost all the major Indian iron ore deposits are of sedimentary and residual origin. They occur in the ore of iron
ore series (Archean) and their equivalents. They are closely associated with the banded-hematite-quartzite (BHQ).
BIF is a sedimentary origin and contains 28-30 % iron. Subsequently the silica of this rock is removed by leaching
and the concentrated iron is left behind to form residual iron ore deposits. These deposits occur in beds which are
up to 40m thick.
❖ Classification of Iron-Ore Deposits
While preparing iron-ore maps of the world, the International Committee under International Geological Congress
standardised the classification of iron-ore. A broad break-up is given below.
1. Metamorphic banded deposits : The major iron-ore deposits of India fall within this group. They are typically
sedimentary or volcano-sedimentary and metamorphosed rocks, consisting of rich iron-ore and siliceous (chert)
bands. They have been differently named in different countries, like Itabirites, Taconites, Jaspilites, Banded hematite
quartzites, Metamorphosed iron-ores etc. Indian iron-ore deposits of Bihar-Orissa belt, Bailadila (M.P.) and those
of Karnataka are typical examples. The metamorphosed equivalent of this rock is banded magnetite quartzite.
2. Continental sedimentary deposits : These are assumed to have formed in fresh water (fluvial or lagoonal) or under
brakish swamp (lacustrine) conditions. Ironstones of Raniganj and Auranga Coalfields are typical examples of this
type of deposit. The ore occurs as layers and lenses of siderite in Gondwana rocks, generally altered to limonite
near the surface.
3. Marine sedimentary deposits such as oolites, detrital, placer and mixed type : The type area is in Lorrain,
France. The Indian example is magnetite deposits of coastal regions such as at Travancore associated with ilmenite
and heavy mineral sand.
4. Volcano-sedimentary deposits : These deposits are related to the volcanic rocks of diabase group of initial
geosynclinal magmatism. The ore-bearing horizons are sub-marine and are bedded. Insignificant minor pockets of
iron-ore in Dras-Thasgam area, Ladakh are the Indian example.
5. Liquid magmatic deposits : They are formed during early crystallization of basic plutonic rocks, mainly by
gravitational differentiation. The typical Indian occurrence is that of titano-vanadium bearing- iron-ore deposits
of Mayurbhanj district, Orissa.
6. Intrusive magmatic deposits : They are related to alkaline rocks of the Precambrian shields. Apatite - magnetite
rocks of Singhbhum represent this type.
Nikhil V. Sherekar 8390377801(M.Sc. Geology GATE+SET+NET-CSIR-UGC-JRF-AIR28)

3. ❖ Distribution
Bihar and Orissa. The iron ore deposits occur in Singhbhum district of Bihar (Titaniferous and vanadiferous
magnetite), and in Keonjhar, Sundargarh and Mayurbhanj districts of Orissa. In these areas the iron-ores are
associated with the banded-hematite quartzites and banded-hematite-jasper. The iron contents of the hematite
ranges from 55-69%. The total reserve is about 5700 million tonnes.
Madhya Pradesh and Maharashtra. Large deposits of iron ore occur in Baster and Durg districts of M.P. and in
Ratnagiri and Chanda districts of Maharashtra. The total reserves of iron ore in this zone is about 3000 million
tonnes. In M.P. the important deposits are in Dhalli Rajhara area of Durg and Bailadila area of Baster. Of these, the
deposits of Bailadila are of special importance. These deposits are one of the most extensive and richest deposits in
the world. The hematite of Bailadila contains 65-68% iron. These deposits are mostly situated on high hills. The belt
of iron ore extends over a length of 35 km and a width of 9 km. The trend of this belt is N- S. The ores are mainly
massive and laminated hematite which change to blue dust at depth. The thickness of the ore deposits ranges between
305 to 610 meters.
Goa. In Goa region the iron ore deposits are closely associated with pink phyllitic horizon in rocks belonging to the
Archaean system. The ore deposits occur in a belt 95 km long and 2 km wide. The iron ore deposits occupy crests
and slopes of hills. At the surface the ore is generally hard and lumpy but in depth it is soft and powdery consisting
mainly of the blue dust. The iron content of the ore varies from 59-62%. The total reserves of iron ore in this area
are about 397 million tonnes.
Karnataka. The iron ore deposits of commercial importance are found in Bellary, Bijapur, North Kanara,
Chitradurga and Tumkur districts. The total reserves of iron ore in this area are about 1450 million tonnes.
Tamil Nadu. Deposits of magnetite are found in Tiruchirappalli and Salem districts. The total reserves of magnetite
are about 447.7 million tonnes.
❖ Reserves
India is endowed with large resources of iron-ore. As per assessment by the United Nations, India possesses 29
billion tonnes of crude ore. However, recoverable ore reserves are limited to less than 50% of the crude. The
recoverable reserves of iron-ores in the country as on 1.4.90 are placed at 9,602 million tonnes of haematite and
3,143 million tonnes of magnetite.
❖ Production and Consumption
The total production of iron-ore during 1990-91 was about 56 million tonnes, of which iron-ore lumps contributed
42%, fines 46% and iron-ore concentrate 12 per cent. Iron-ore industry is basically an export-oriented ne. Of the
total despatches of 54 million tonnes, 31 million tonnes (57%) were reported for export. Japan, Korea Republic,
Romania and China are the main countries where iron-ore is being exported. The average metal content of the ore
produced was about 64% Fe. Goa remained to be the leading producer accounting for 24%, followed by Madhya
Pradesh and Karnataka 22% each, and Bihar and Orissa 15% each. The remaining quantity was contributed by
Maharashtra, Andhra Pradesh, Rajasthan and Haryana. During 1989-90, about 20 million tonnes of iron-ore was
consumed in different industries. The producers of pig-iron and steel are the main consumers of iron-ore (about 95%
of total consumption). The sponge iron units, cement, alloy steels, ferro alloys, foundries, electrode industries and
coal washeries are the other consumers of iron-ore
❖ Uses
Iron found its industrial use first time in 800 B.C. which marks the commencement of "Iron-age". The Iron-age
culminated in "Steel age" in the nineteenth century with steel gaining the importance.
1. The iron-ore is basically used for the extraction of iron-metal in the form of cast-iron, wrought iron, steel and
iron-alloys which have their own particular uses.
2. It has a major role in building construction, farm tools, machines, rails railway wagons; automobiles, ships etc.
3. The other use of iron ore is in coal washery as a medium for flotation. It is also used in certain industries like
cement to make up the proportion of iron in the raw material under water cable sheathings, powder metallurgy
etc, the quantity so used in these ways is insignificant compared to its use in iron smelting.
4. Iron ore is mainly utilised for making pig iron, sponge iron and steel.
5. Most is used to manufacture steel, used in civil engineering (reinforced concrete, girders etc) and in
manufacturing.
6. Cast iron contains 3–5% carbon. It is used for pipes, valves and pumps. It is not as tough as steel but it is cheaper.
Magnets can be made of iron and its alloys and compounds.