Name_____________________
Economic Geology
Magnetite crystals (iron ore, Fe3O4)
Economic geology is concerned with earth materials that can be utilized for
economic and/or industrial purposes. These materials include precious and base metals,
nonmetallic minerals, construction-grade stone, petroleum, coal, and water. The term
commonly refers to metallic mineral deposits and mineral resources. The techniques
employed by other earth science disciplines (such as geochemistry, mineralogy,
geophysics, and structural geology) might all be used to understand, describe, and exploit
an ore deposit. Economic geology is studied and practiced by geologists; however it is of
prime interest to investment bankers, stock analysts and other professions such as
engineers, environmental scientists and conservationists because of the far-reaching
impact which extractive industries have upon society, the economy and the environment.
Mineral processing, otherwise known as mineral dressing, is the practice of
extracting valuable minerals from their ores. Industrial mineral treatment processes
usually combine a number of unit operations in order to liberate and separate minerals by
exploiting the differences in physical properties of the different minerals that make up an
ore. An ore is a volume of rock containing components or minerals in a mode of
occurrence that renders it valuable for mining. An ore must contain materials that are
valuable, in concentrations that can be profitably mined, transported, milled, and
processed, and able to be extracted from waste rock by mineral processing techniques.
Ore deposit is a term applied specifically to those economic mineral occurrences which
could be mined at a profit after consideration of all factors impacting a mining operation.
Ore grade is a measure that describes the concentration of a valuable natural material
(such as metals or minerals) in its surrounding ore. Ore grade is used to assess the
economic feasibility of a mining operation: the cost of extracting a natural material from
its ore is directly related to its concentration, and the cost of extraction must be less than
the market value of the material being mined for the operation to be economically
feasible, this process is known as an ore assay. Ore minerals are generally oxides,
sulfides, silicates, or "native" metals (such as native copper) that are not commonly
concentrated in the Earth's crust or "noble" metals (not usually forming compounds) such
as gold. The ores must be processed to extract the metals of interest from the waste rock
and from the ore minerals.
Iron ores are rocks and minerals from which metallic iron can be economically
extracted. The ores are usually rich in iron oxides and vary in color from dark grey, bright
yellow, deep purple, to rusty red. The iron itself is usually found in the mineral form of
either magnetite (Fe3O4) or hematite (Fe2O3). Magnetite, having a certain characteristic
physical property, as the name suggests, it is magnetic, and this property can therefore be
utilized in the extraction and processing of this mineral from its parental rock. Here, you
will utilize a magnetic separation technique, in order to determine the ore grade of three
magnetite deposits, and whether or not each deposit is economically feasible to mine.
Laboratory Procedure
For the three given ore deposit samples, first weigh the entire sample as given,
and record your observations in the chart below (A). Next, dump out the entire sample in
the given trays and spread out evenly. Sweep the cylindrical magnet around in the
sample, such that it begins to separate out all of the magnetized iron ore material
(magnetite), which is strongly attracted to the magnet. Carefully remove all of the
gathered magnetite off of the magnet and place it back into the container. Repeat this
process on the remainder of the ore deposit until you’re fairly certain that you have
gathered all of the magnetite from that deposit. Weigh and record the weight of just all of
the magnetite you had just extracted from the ore deposit. Finally, determine the weight
percent (wt%) of magnetite in the deposit (weight of extracted magnetite / weight of
whole deposit, x 100). Repeat this process for the other two samples. Do not mix the
samples! Work with one sample deposit at time, and return it to the proper container
before dumping the next. Determine if each of the three ore deposits would be
economically feasible to mine, i.e. if the market price of the ore is greater than the price
of extraction, such that, mining of that deposit would turn a profit.
Deposit A
Deposit B
Deposit C
(A) Weight of raw material (g)
(B) Weight of iron ore (g)
(C) Weight of waste rock (g)
((B/A)x100) Weight percent of ore (wt %)
The cost of extraction per ton (2,000lbs) of raw ore material is roughly $2,000,
and the market price per pound of iron ore is $2. If the given amount of sample for each
of the ore deposits (raw material) were scaled up to represent one (1) ton, would these
iron ore deposits be economically feasible to mine?
Deposit A
Lbs of ore per ton of raw material
(ore wt% of 2,000lbs)
Market price per deposit (lbs x $2)
Economically Feasible? (>$2,000)
Deposit B
Deposit C
Mineral flotation (also froth flotation) is a process for separating valuable
minerals from (waste) gangue minerals by taking advantage of differences in their
densities. Density differences between the two are used to separate them using heavy
liquids. Heavy liquids can be any liquid substance with a density usually denser than
water (density > 1.0 g/cm3). The density of the liquid is generally chosen based on the
densities of the valuable minerals and gangue minerals. If the valuable minerals are less
dense than the heavy liquid, they float on the surface, and only need to be scooped off to
be separated. The denser gangue minerals sink to the bottom and are disposed of. If the
valuable minerals are denser than the liquid, they sink to the bottom, where less dense
gangue minerals float to the top, are disposed of, and the valuable minerals collected off
of the bottom. The flotation process is used for the separation of a large range of
sulfides, carbonates and oxides prior to further refinement. Phosphates and some coals
are also processed by flotation technology.
Laboratory Procedure
For the two given coal sample deposits, first measure the volume of the entire
sample, and record your observations in the chart below (A). Place the entire sample
back into the container and fill the graduated cylinder about halfway full of water. Next,
dump out the entire sample into the graduated cylinder filled with water. All of the
denser coal should sink to the bottom of the cylinder, while the less dense gangue mineral
floats to the surface. Record the volume of coal in that sample (B) and the volume of the
waste gangue mineral (C) below. Finally, determine the volume percentage (vol %) of
coal in the deposit (volume of extracted coal / volume of whole deposit, x 100). Once
finished, hold a screen securely over the top of your cylinder, such that you can pour out
the water yet the material stays in. Place all of the material back in the original container.
Coal Deposit A
Coal Deposit B
(A) Volume of raw material (mL)
(B) Volume of coal (mL)
(C) Volume of waste rock (mL)
((B/A)x100) Volume percentage (%) of coal
Determine if the coal deposit would be economically feasible to mine. The cost
of extraction per ton (2,000lbs) of the raw material is roughly $1,000, and the current
market price per pound of coal is $1. If the given amount of sample for the coal deposits
(raw material) were scaled up to represent 1 ton (2,000 lbs), would this coal deposit be
economically feasible to mine?
Coal Deposit A
Lbs of coal per ton of raw material
(coal vol % of 2,000lbs)
Market price per deposit (lbs x $1)
Economically Feasible? (>$1,000)
Coal Deposit B