Welcome to this lecture series on mineral
resources. Mineral resources are essential
for
the economic development of any country. Take
the case of the developed countries like
United States, Canada, Australia and so on,
in these countries, the initial phase of their
economic development largely was contributed
by their mineral resources which they
exploited for the development of their industry.
In the Indian context the scenario is not
that very distinct as regards to the role
of mineral
resources in the initial phase of development
of the economy. And still we lack resources
of many of the important metals like the precious
metals, base metals and critical metals
for energy resources and we have to largely
depend on import of these metals from other
countries. So, there is a need for the augmentation
of the available mineral of the mineral
resources for better economic development
and industrial growth.
So, this course is essentially a first level
undergraduate level course, and it is taught
in
many universities and institutes by different
course names as economic geology, ore
geology. And in this course we will in this
lecture series; it will be more conceptual,
but
not much not involving much of mathematics.
What all little mathematics, we will have
towards the later part only high school level
mathematical knowledge and capabilities
will be sufficient.
So, the concepts and facts figures that will
be discussed here; have been taken from
available textbooks like the book by Jensen
M L Jensen and Bateman, and by Anthony M
Evans, Laurence Robb - Introduction to Ore
Forming Process and the book by Craig
Vaughan and Skinner on Resources of the Earth.
Mineral Resources Economics and
Environment by Stephan Kessler, and Ore Deposited
Geology by John Ridley, and
Understanding Mineral Deposit by K. C. Misra.
Although we will use various other
resources and other materials and we will
be indicating in the due course of the lecture
series.
So, let us have an overview. So, this course
is, the objective of this course is to give
an
overview of the subject, and the very first
aspect of mineral resources is the geology.
So,
it is
basically the science of mineral deposit formation
and tries to answer very
fundamental queries as to how these mineral
resources form, where they formed, when
they formed and trying to understand the rationale
behind availability or distribution of
these mineral resources across different continents.
Once we are equipped with the
scientific knowledge about the mineral resources
and their formation this can be very
effectively utilized for exploration of this
mineral resources in areas where they are
not
known to be existing as of now.
The another important aspect of mineral resources
involves their exploitation, use of
technology and different methods, scientific
methods for exploitation of these mineral
resources once they are discovered. Since,
it does not follow the purview of geology
this
is rather the activities of the mining are
done by the mining engineers. So, we will
not be
covering much from this aspect.
Then we will see these mineral resources are
essentially economic commodities, we have
to see how effective policies should be formulated
for their exploitation in a sustainable
manner. And we need to have, we need to formulate
proper policies for their exploitation
and to sustain for the future.
Mineral resources exploitation also does affect
the environment in many ways starting
from the time that they are being explored.
And once they are discovered, the
exploitation processes, the several downstream
process and extraction of these metals
and the various ways that the exploitation
and the extraction process downstream
industrial process involving the minerals
metals, they affect the environment, the
ecology.
And we have to see as to how such type of
effects could be at least evaluated, and
whether there are remedial measures which
can be taken for the deleterious
environmental impact and that also is our
responsibility. So, these are the four aspects
that we plan to cover in this lecture series.
As we all know we can define minerals as inorganic
crystalline solids. So, minerals could
be they do occur in nature, but they can also
be synthesized in laboratory. So, the missing
of the term natural is intentional here, we
can take them as inorganic crystalline solids,
they are the minerals of different metals
as we will see the classification. So, resource
is
an economic term this is essential for economic
development as I have already discussed.
So, now we can say that minerals which are
either direct raw materials for various
industries we know what the industries are,
industry, the
infrastructure industry, the electrical and
electronic industry, transportation industry,
aviation industry, refractory fertilizer and
so on and so forth. So, all industries either
directly or indirectly, it depend on mineral
resources as either the direct raw material
for
them or after the metals are extracted from
the minerals, they are used in different
industries. So, when these two are combined
minerals with a direct raw materials for
various industries, and those containing elements
or metals of high economic value are
our mineral resources which we will be discussing
in this lecture series.
We all know why materials are so much sought
after. The metals, for example the
transition metals, the precious metals like
gold, platinum of group metals, platinum,
palladium, osmium, iridium. And many of the
metals like tin, titanium, vanadium and so
on these metals have got very special properties,
their electrical conductivity, thermal
conductivity, malleability, ductility and
so many other properties which make them very
special and suited for many industries, many
of our products for the modern technology.
That is the reason why these metals are so
much sought after. But also the non-metals,
the non-metallic minerals are also equally
important as we will be seeing them.
So, we can divide the mineral kingdom broadly
into two categories, the silicates.
Silicates are the common rock forming minerals
making up the bulk of the Earth’s crust,
often they are used as raw materials for industries
such as the glass, ceramic, refractory
industry. And they do, they are constituted
of the Si O 4 fundamental tetrahedral building
blocks which combine in many different proportions
to give the range of silicates as you
have already studied in your elementary level
courses. The nesosilicate, sorosilicate, ino
silicate, phyllosilicate, tectosilicate and
so on.
Some of the minerals like silica Si O 2 is
a raw material for glass industry and many
of
the clays are raw material for ceramic industry.
The alumino- silicate, kyanite sillimanite
and andalusite are raw materials for the refractory
industry and so on. And we know that
they are economically important even though
they may not be as very economically
valuable as the metals. The non-silicates
they mostly constitute the mineral resources
as
we see them here.
The oxides or the hydroxides of metals like
aluminium, iron, titanium, chromium,
manganese, tin and uranium. And they are either
the primary minerals forming in
different environments or sometimes the product
of oxidation of this kind of mineral
bodies when they are exposed to the surface.
And metals like aluminium, iron, titanium,
the bulk of the ore minerals are the oxide
minerals.
The carbonates : no much of metal carbonates
are important as mineral resources; but
that it also sometimes the primary ore minerals
get oxidized in the surface in the
presence of carbon dioxide to give the carbonates.
Some of them like the calcium
carbonate which is an important with constitutes
the limestone is an important raw
material for cement industry.
The sulfides : these constitute the most important
class of the ore minerals, which we
will see in a short while. Most of the transition
metals and some of them other base
metals, and the semi metals they do form their
sulfide their minerals which are sulphides
when they constitute the resource. The halides
as we all know them the rock salt.
So, phosphates : mainly thorium and the rare
earth elements are available in the form of
phosphates and apatite being one of the minerals
which is an important material for our
fertilizer industry. And we also do look for
such kind of minerals. Tungstates, this whole
a mineral for tungsten. And also the native
metals for example, the noble metals like
gold
and platinum, they do occur in their native
form because and metals like copper also is
available sometime in a native form under
some special conditions. And as far as the
non metals are concerned, sulfur which is
an important resource for fertilizer, it will
be
less for many medicinal purposes. And carbon
which is essentially where it is presented
gemstones diamond. So, these are the some
of the examples of native metals.
But these minerals, their immediate implication
that you can see from here is that
whenever such kind of minerals are forming
under any kind of an environment, they do
indicate some specific physicochemical parameters
of the environment in which, they are
forming.
For example, for the oxides to form, we need
to have an environment where the
oxidation states should be favourable or to
have appropriate partial pressure of carbon
dioxide to form the carbonates. And sometimes
we find that these minerals, as will be
discussing in the attributes of the mineral
resources, mineralogy of the mineral resources
constitute a very important aspect.
This is e one of the very fundamental contribution
to science. This is the periodic table of
elements, which guides us in understanding
many of the chemical phenomena anywhere.
And since we are interested or the focus of
our subject is mineral resources, information
of this mineral deposits we can always get
some insight by looking at the periodic
classification of elements.
Here this periodic table has been taken from
the book of Stefan Kessler, where you see
the elements are differently shaded - the
nonferrous metals here, the elements for
fertilizer sodium, potassium, calcium;
nitrogen of course, is coming from the
atmosphere, phosphorus and sulphur. Here are
the semi metals arsenic, antimony and
bismuth, the metals like tin and lead. This
cionage group of metal copper, silver, gold,
the platinum group of metals, the transition
metal and the rare-earth.
Even though we can always go on studying it
for very much minute details as possible
but to be brief, say for example, a metal
like chromium. It is very rigidly occurs in
only
plus 3 oxidation state in the primary rock
forming cycle, although chromium also forms
it plus 6 in different specific surface environment.
So, that is why this metal chromium
occurs, is very very restricted in its occurrence,
in its type of because it forms only one
ore mineral that is chromite, and it also
does form a very restricted type of mineral
resource.
Metals like a manganese occurs in variable
oxidation states from plus 2 to plus 7, but
it
generally occurs in its oxides in mineral
resources. It is manganese oxides which is
recovered as the ore mineral. Metals like
iron has equal affinity for sulfur as well
as
oxygen. So, it occurs as pyrite which is the
major sulfide mineral of iron which is iron
suflide pyrite. And also is oxide which constitute
the major bulk of the ore.
The metals like zinc, cadmium, mercury, copper,
and the semi metals this arsenic,
antimony and bismuth essentially they form
their sulphides. Amongst the high field
strength elements like titanium, vanadium,
zirconia, hafnium tantalum they form their
oxides, in exception to molybdenum which forms
its sulphide.
And the first series rare earth elements,
lanthanides they are mostly forming in the
common rock forming minerals or as phosphate
that is the important resource of Th.
They are very interesting alloying property
for which they are very much sought after,
for improving the magnetic properties of alloys
they are very much used, very much
sought after.
And the classification like say for example,
carbon is both a source for energy as well
as
precious gems as we know it occurs as diamond
and so on. And the fertilizer industry,
construction industry, these elements which
you can we can see from the classification
here.
Elements of the periodic table in context
of mineral resources, also are geo chemically
classified to lihophile, siderophile, chalcophile
and atmophile. Lithophile elements
generally have the tendency to get enriched
in the earth’s crust on formation in the
rock
forming silicates. They do constitute many
of the large ion lithophile elements like
lithium, potassium, rubidium, cesium and so
on. The siderophile metals are the ones
which have the maximum affinity for iron,
which is marked over here in blue they are
the siderophile elements.
The implication is that during the fractionation
of the bulk earth to core and mantle when
most of the iron and nickel went to the core
many of these siderophile elements like the
platinum group of metals and gold also were
partitioned or fractionated into the earth’s
core and that is how their availability in
the mantle was greatly reduced. And as shown
in
the previous figure from the periodic table
you could see the chalcophile metals.
So, they are the ones which occur as the sulphide
minerals and recovered from nature in
the form of their sulfides. Atmophiles are
the noble gases which we do not consider them
in the present scenario. So, these geochemical
classification of elements help us in
getting first hand information about the mineral
resources, what type of minerals to
expect in what kind of geological environment.
This diagram has been taken from the geochemical
earth reference model database. Here
of the x-axis is the abundance. The atomic
number are plotted from one to just above
90
up to uranium. And on the y-axis, the abundance
of these elements in reference to to the
power 6 atoms of silicon have been plotted.
The zigzag pattern in the abundance of these
metals is a very fundamental principle that
odd atomic number elements are less
abundance than the even the atomic number
elements.
And the ones which are the most abundant elements
the rock forming elements are
shown over here. The rarest metals ruthenium,
rhodium, palladium, gold, platinum as we
saw in the previous diagram are the rarest
minerals. The blue ones are the rare earth
metals which occur in much less amount compared
to the other metals. The metals are
plotted on log scale.
Now, as far as the mineral resources are concerned,
the fundamental questions that we
ask that in what quantity we actually get
them. And this diagram here is it shows the
relationship on the x-axis, we will have the
log abundance on the bulk continental sorry
bulk continental crust. Where the order of
about 9 order of magnitude variation means
10
to the power of minus 8 to nearly 10 where
you could see the abundant metals like
aluminium and iron having abundance is almost
is 8 percent and 5 to 6 percent in the
continental crust. And on the y-axis, the
quantity of these metals available as mineral
resources in terms of metric tons and 1 ton
is 1000 kg, are plotted here. That is also
on
the log scale. We also see that they vary
all most of the in beyond the similar about
8 or 9
orders of magnitude in the quantity of these
metals starting from very scarce metal like
rhenium to going up to aluminium and iron
which are available in billions of tons of
such
mineral such resources taken all together.
They are occurring in the earth.
So, this diagram gives us a first very first
insight that the total quantity of any particular
metal that is available as a resource is has
some kind of a relationship direct relationship
with their abundance in the continental crust.
And the diagram onto the left is a vertical
scale where a term that is written here is
‘enrichment factor’ which is mentioned
here.
And the element the metals of interest are
plotted on this or are shown on this vertical
scale starting 1 to 100000.
We see, abundant metals like aluminium and
iron have enrichment factor values which
are less than 10, we can say the less than
1 order of magnitude. What is it tell us?
It tells
us that an abundant metal like aluminium and
iron does not only needs to be very little
enriched to give its to be available as resource
which you can exploit. And it is very
scarce metal like mercury, whose crustal abundance
is of the order of 10 to the power of
minus 5 in weight percent. would require almost
about 80,000 or more 
times enriched so
that it will be available to us in the form
of a resource.
It does give us some few more insights that
the processes, so that means, if we when will
be looking at the different earth processes
that is what we basically try to correlate
here,
all the earth processes to formation of mineral
deposits. Then we see that the this scarce
metals like mercury possibly we would be needing
multiple steps or multiple stages of
enrichment so as to reach to a level where
we can call them a resource and the metals
in
between fall. They do also are tell us at
least at the first hand that these metals
we will
definitely take longer time to be available
as resources in the earth.
Now, let me tell you, when we use the word
resource it is a putt generalized qualitative
term giving representing the total for any
particular metal or a mineral. What actually
it
comprises is the mineral or the ore deposits.
These are discrete entities present that we
see them and measurable in the quantity. They
do satisfy some quality and quantity
parameter. And the question is that where
actually do we find them. So, the answer is
that
we find them in the earth’s crust or to
be more specific in the upper crust.
So, what are the crustal domains in which
we get these ore deposits? These mineral
resources, they occur in the crust more specifically
in the upper continental crust either
exposed on the surface or even going to depths
as high as 5 kilometre. Quickly we can
see what are the different crustal domains
that we can expect to see such mineral deposits
occurring.
They will be occurring in recent or ancient
sedimentary basins, they may be occurring
associated with magmatic bodies, subsurface
intrusive magmatic bodies in crustal scale
brittle ductile deformation zones. It could
be crustal scale as well as local scale
deformation zones such as shear zones, fracture
zones, folded strata and so on. And these
sedimentary basins also could be the marine
sedimentary basins or the fluvial 
and so on.
So, we will see them, the whole spectrum in
the due course of this lecture.
And let us try to look at some of the basic
terminologies. What you mean by this mineral
deposits that we are talking about, is essentially
constituting of some entity which you
can call as an ‘ore,. So, we defined ore
as a natural aggregate. Ore essentially a
rock it
constitutes of natural aggregate of minerals.
And the only speciality is that in the ore
there is the concentration of either one or
more than one element is above a threshold
or
a background value which is called as a Clarke
Value after the famous geochemist FW
Clarke. It is kind of an average value concentration
in there in the crustal rocks.
So, these are examples of ore. This is taken
from the iron ore, this one photographs from
the Hamersley Basin in Australia where I could
see the darker bands constituting of
hematite and the lighter band with the red
bands are the cryptocrystalline ferruginous
silica known as chart. And in this we all
know that this black this grey band which
is the
iron oxide is the material for interest and
we call the if that is the ore mineral then
the
part which we would like to discard is the
gangue mineral.
This is a specimen of ore from Malanjkhand
copper deposit in central India where you
could see these as the sulfide minerals of
copper in a matrix of quartz. And here the
quartz is the gangue mineral and these are
the ore minerals. And if for in order for
this
material to be qualify to be called as an
ore, here we know that this concentration
of
metals like copper has to be above a certain
value. Say for example, at least of a 0.45
percent of copper to be for this material
to be called as an ore.
So, this ore when we call that an ore comes
from something which is an entity occurring
in the association with common rocks in the
crust which is an ore body. This is an
example of the ore body of copper from Malanjkhand
copper mine in Central India.
Where you see it is a rich mineralization
of copper sulphide copper iron sulphide
chalcopyrite mineralization in this ore body.
So, the ore body it needs to be present in
a
required dimension - length breadth and thickness.
So, that it gives us certain point
certain quantity of the metal for that to
be feasible to be recovered by utilize by
using our
process different scientific methods for extraction
of a recovery or this particular metal.
So, this is the example. So, when we see this
is a typical look of a mine where an ore
body is being exploited. This is taken from
the Malanjkhand mine. And if we want to
represent the ore body in space we can only
do it on a geological map. So, it is very
very
important that if we want to understand the
ore deposit formation processes, we do have
to look at their maps at all scales.
This is a mine scale geological map where
the ore body which is basically the copper
rich ore body extending for a length of almost
like 1.8 to 2 kilometer in surrounding
rocks in association. As I told you that they
occur in association with common crustal
rocks. This is what is an example of a mine
in scale geological map. If we take a
subsurface section of this ore body we do
we do see that it does extend to depths that
is
what exactly what I mentioned that this occurrence,
they do sometimes they do either do
they are exposed or they do extend to a great
depth in the subsurface - variable depths.
And when such ore deposit they can either
occur independently in one geological terrain
or there could be lots of such deposit occurring
together this one example this is from the
Nomaundi Basin in Singhbhum Craton. In this
particular basin itself we get a good
number of localities where the iron ore is
being mined. In addition to that, there are
many
manganese the local it is where the manganese
ore is also being mined. This is an
example where and the this is an example of
a place where there are several such ore
bodies can occur in a small area of just about
a square kilometre, which is coming from
the Ekati diamond mine in Canada.
And several such in those cases we call them
as ore district or mineral province or
mineral belt or mettallogenic province. There
are many such examples of such kind of
mineral belt mettallogenic province, the classic
examples come from the Abitibi
Greenstone Belt in Canada, Kalgoorlie Gold
District, Yilgarn, Craton in West Australia,
Carlin Trend in Neveda, United States of America
where it is a very rich zone producing
gold ores and the gold bearing Scist belt
in Dharwar craton. These are some of the
examples of the mettallogenic province or
mineral belts. So, we will continue discussing
about these mineral resources in the subsequent
classes.
Thank you.
