My Guyana El Dorado – How we get the gold

Gold, as a precious metal, has been valued and held in high esteem since ancient times, and remains one of the most highly prized metals that have, throughout the ages, been used to symbolize wealth and power, and keep commerce going.

Guyana Times Sunday Magazine interviewed Guyana Geology and Mines Commission’s Manager of Special Projects Sydney Edwards, who spoke about how the precious and valuable metal is mined.

“Guyana is located in a Precambrian Shield, and an area in that shield will have gold. The Precambrian Shield is an extensive structural unit of the Earth’s crust composed of exposed basement rocks formed during the Archean or Proterozoic eons, which together comprise the Precambrian Era, ending 544 million years ago.

“We have come to know of this due to our geological testing. We know from the geology of Guyana that there are gold-bearing areas, due to our testing. Areas like in Mazaruni, we know gold is there, hence a lot of miners are located there. Gold isn’t a renewable asset – once it’s exploited it’s gone. Now they have to go down as deep as 4000 feet to get gold. Our testing is done by means of a coring drill to test and examine rocks thousands of feet in the Earth to determine what is going on down and what metals are there,” he said.

“Gold is a metal that occurs in a natural state in the crust of the earth. We get minerals from two sources – it’s either grown or mined. Mining is the extraction of minerals, and the demand and scarcity of it determines the price for it. Gold is four times heavier than iron, and that is a property that is used in the extraction of gold. Gold is extracted in what one may call gold dust or nuggets. Gold is a rare metallic element that is found in natural settings, mostly in veins of quartz and in certain other alluvial deposits. It can be found in a free state or in combination with other metal. Gold mining consists of the processes and techniques employed in the removal of gold from the ground,” he noted.

Gold extraction

Edwards said that there are several techniques by which gold may be extracted from the earth. In Guyana, gold mining is mainly by the open-pit method – which refers to extracting rock or minerals from the earth by their removal from an open pit or borrows. Open-pit mines are dug on benches, which describe vertical levels of the hole. Most walls of the pit are generally dug on an angle less than vertical, to prevent and minimize damage and danger from rock falls. This depends on how weathered the rocks are, and the type of rock, and also how many structural weaknesses occur within the rocks, such as a fault, shears, joints or foliations.

Another method Edwards mentioned is dredging. Dredge mining is the mining of sediment deposited from flowing water, such as gravel, sand, and rock, to collect the gold. Generally, the sediment is suctioned up from the bottom of a water body, or buckets are used to scoop up the sediment. Dredge mining is the technique that is often used by commercial and recreational miners to collect raw gold. When dredge mining for gold, the dredge is used to dig, sort the materials, collect the gold, and discharge the unwanted sediment.

“Gold panning is another method and is mostly a manual technique of sorting gold. Pans that are wide and shallow are filled with sand and gravel that may contain gold. The pan is submerged in water and shaken, sorting the gold from the gravel and other material. As gold is much denser than rock, it quickly settles to the bottom of the pan. The panning material is usually removed from stream beds, often at the inside turn in the stream, or resting on the bedrock bed of the stream, where the density of gold allows it to concentrate. This type of gold found in streams or dry streams is called placer deposits,” he said.

Sluice boxes are also commonly used in our gold mining system. A sluice box is essentially a man-made channel with riffles set in the bottom. The riffles are designed to create dead zones in the current to allow gold to drop out of suspension. The box is placed in the stream to channel water flow. Gold-bearing material is placed at the top of the box. The material is carried by the current through the box where gold and other dense material settles out behind the riffles. Less dense material flows out of the box as tailings.

Another mining process is amalgamation. This is a mercury-based process which works because of gold’s willingness to be dissolved by mercury. The mercury is applied on an ore, picks up the gold, and the resulting amalgam is distilled, with the mercury being boiled off to remove it. Mercury is highly toxic and therefore environmentally sensitive, making the industrial plant to perform this type of extraction expensive. Edwards stated they are moving away from this method because of mercury’s danger to health, so miners utilize the other safer methods.

Grading gold

Gold is graded in carat. A carat is a measurement of the fineness of gold. The grades of gold reduce in karat fineness as more non-gold metals such as alloy are mixed with gold. Pure, fine gold is very soft and does not lend itself well to gold objects that receive a lot of wear, as pure gold wears easily.

The next grade down from pure gold is 22-carat gold which is somewhat harder but is still easily worn away, especially if in contact with gold of lower grades. The 22k gold is used in some gold coins and investment jewellery. The 18-carat gold is used for high quality jewellery. It is considerably harder than the two previous grades but still wears more easily than 14 carat grade gold and lower grades of gold. The 14 and 12 carat gold is the most commonly used in Guyana.

The environment

Extracting gold from the earth inevitably means destruction of the natural environment – something that often creates discord between the need for economic growth and sustainable use of our natural resources.

It is an issue constantly engaging the government and miners, and one that fuels the debate on how to balance livelihoods with the environment.

As Edwards pointed out, gold isn’t a renewable asset – once it’s exploited it’s gone.

For the past year, the country mined more than 311,000 ounces of gold for export, proving that Guyana is indeed our El Dorado.