gold mining has changed dramatically in the last 150 years
in the heady days of the gold rush a person could pan or sluice in a stream for
nuggets of gold today mining is a large-scale activity that involves a lot of
talented men and women large earth-moving equipment and sophisticated processes
but gold isn't as easy to get as it was in the gold rush days quite often
deposits mined today contain only microscopic bits of gold invisible to the
naked eye so many tons of rock have to be mined and processed to produce gold
that you can see in use that's why modern gold mines are typically large it's
also why so many people work at the mines mines offer a spectacular array of
jobs and opportunities the active life of a mine can range from a few years to
more than 50 years workers safety is of the utmost importance and the industry
is very strong today we're going to show you an active modern goldmine mine
goes through four stages or life cycles first there is exploration of new gold
deposits second there is mine planning third there is mining and processing and
finally there is reclamation before any actual mining can begin a process known
as exploration has to happen geo scientists study the earth and its geological
makeup to look for signs of gold deposits geologists are people who study rocks
and the earth these people are the ones who helped start the mining process
first they study rocks and make maps of a region as they progress they use more
complex methods of finding out what is below the surface of the earth using
geophysics and geochemistry geologists start creating maps that show their
estimate of a potential gold deposit to test the estimate poles are drilled to
identify where gold is concentrated after collecting enough samples and data
the geologists can generate a 3d model of the ore body this model shows areas
within the ground that contain various concentrations of gold with this model
geologists and mine engineers can define a mine plan mine planning is a complex
and sophisticated process it involves experts in nearly every field every cost
is calculated and every detail is evaluated in addition environmental
conditions and resources are considered during the exploration and mine
planning stage an environmental baseline is taken of the proposed area of the
mine this environmental information is used to determine potential impacts to
the land develop reclamation plans and prepare permit applications before
mining begins permits covering all aspects of the mine must be issued this
information is also used to determine the impact on people and the local
communities mines take an active role in communicating with local organizations
and groups who have a vested interest in the company and the operations the
relationship between a mine and a community is very important using the
geologic model a blasting plan is developed this plan is used by the drill and
blast crews to layout and drill a pattern that will safely and effectively
fracture the rock for mining drill rigs drill hundreds of holes in a specific pattern
for the blast then the blast crew loads each hole with a blasting agent called
ANFO or ammonium nitrate and fuel oil the blast Foreman clears the area sets up
roadblocks to ensure worker safety starts the warning siren and calls fire in
the hole the blast fractures thousands of tons of material hydraulic shovels
and front-end loaders load the rock in the haul trucks these haul trucks hold
about 240 tons of ore that's 480 thousand pounds that's as heavy as 200 cars or
is rock that contains a concentration of a valuable mineral in this case gold
that can be mined at a profit because the geologists studied the rock before
the blast they know which areas of the blasted material contain high or low
grade ore while our material may look similar the concentrations or grade of or
within the material are different the people who work in the assay lab
determine these differences by subjecting or samples to various tests
high-grade ore has more gold particles than low-grade ore grade is used to
determine how the ore will be mined and processed ores can also vary in
chemical makeup these factors also play a big part in determining how the ore
is processed so that's why each block of ore in a mine is referred to by its
grade Rock not containing sufficient concentrations of gold is referred to as
waste rock each block is mined out separately and delivered by haul trucks to a
specific area of the mine site for processing or placement in a waste rock
facility if the ore is low-grade then it goes to a leach pad if it is high-grade
then it goes to a mill autoclave roaster or other processing facility a leach
pad is a large pile of low-grade ore carefully constructed on top of a
specially designed liner that looks like a giant thick sheet of black plastic
this impermeable liner and the deep layers of other dense materials on which it
lays prevent the leaching solution from entering the ground below a long
network of hoses drips a weak cyanide solution onto the or the gold in the ore
is dissolved by the cyanide solution and trickles down to the bottom of the pad
the solution collects in a man-made reservoir and is then pumped through a
series of tanks containing carbon particles the dissolved gold sticks to the
carbon particles which are later separated from the gold in a stripping process
the resulting gold solution moves on to another process stage high-grade ore is
sent to either a mill autoclave or roaster the mill grinds the ore into a fine
sand to prepare it for the final processing stages that turn the scattered
invisible gold particles and to solve it masses of gold that you can see some
gold or needs more processing before it can go through these final stages which
include a form of carbon leaching similar to that used for the lower grade or
from the leach pads this is the case for ore that has sulfites in the rock
making it untreatable in the mill the roaster removes the sulfides so the ore
can be effectively processed through carbon leaching process facilities like a
roaster generate tremendous Heat water that is circulated through the plant to
help control temperatures often generates large amounts of steam like you see
here an autoclave is used to remove sulfides from certain types of ore the
auras first wet ground and then put through the autoclave where high heat and
pressure are applied eventually all processed or ends up in a solution called a
slurry which moves through a series of tanks containing a mixture of weak
cyanide solution and carbon the gold bonds to the carbon which is separated
from the slurry the carbon now loaded with gold is further processed to remove the gold and put it into solution the gold solution is then sent through a
circuit where the gold is recovered through an electrochemical process similar
to the process used to make chrome-plated car parts the recovered gold is then
melted in a furnace at 2100 degrees Fahrenheit and pour it into molds to form
gold bars however these bars called door a bars are a mixture of about 85% gold
and 15% silver they are sent to a European refinery to be refined into pure
gold bullion areas that are no longer needed for mining are reclaimed when
possible this reclamation is done concurrently or while mining continues nearby
after mining ends the entire mined site is reclaimed or returned to a
natural-looking appearance so that after a few years it will be difficult to
tell that any mining took place at all Gold is a vital important metal around
70% of gold demand is for jewelry 11% is for industrial use in fields such as
dentistry and electronics and 13% is used for gold bars and gold coins that
institutions and individuals use for investment gold is used for all sorts of
medical and technological applications almost all electronic consumer items
like mobile phones computers and flat-screen televisions contain a small amount
of gold which is critical to the reliable and efficient function of the
equipment the chips and contacts found in a car's anti-lock braking system all
contain gold as do the electronics controlling the inflation of car airbags in
the event of a crash smoke detectors routinely used in millions of households
to protect against fire contain a gold alloy placed between layers of another
metal it's fair to say that without the use of gold all these products would be
much less efficient and reliable than they are now mining is a business that
needs the dedicated minds and hands of thousands of people each person on a
mine site holds an important job that is crucial to the mining process without
this skilled group of hard-working people mining just wouldn't work as you have
just seen mining involves many steps every part of the process is important in
producing gold and the final product is well worth the hard work thank you for
watching this brief presentation on how gold is produced we hope you take the time
to learn more about mining and its opportunities.
