Geologists have developed different theories about the formation of gold deposits in the Earth’s crust. They are still not sure which theory is correct or whether a number of different processes worked together to account for the ways gold is deposited in the Earth’s crust.

One theory suggests that gold particles settled to the bottom of an ancient sea, along with clay and sand. Over millions of years these sediments compacted, hardened, and turned into rock. The individual gold particles were then trapped within layers of solid rock. When the seas evaporated and the land shifted and collided, these layers of quartz and slate fractured and folded, producing hot fluids that migrated through the rocks and dissolved the gold. The gold was then deposited in quartz veins nearer the surface of the Earth.

Another theory proposes that gold was formed millions of years ago deep in the Earth. Through the movement of the Earth’s plates and volcanic activity, gold was dissolved in hot fluids and gases and then forced upwards by heat and pressure. Periodically, over millions of years, it was forced into cracks and fissures in the Earth’s mantle, of Read More
Geologists have developed different theories about the formation of gold deposits in the Earth’s crust. They are still not sure which theory is correct or whether a number of different processes worked together to account for the ways gold is deposited in the Earth’s crust.

One theory suggests that gold particles settled to the bottom of an ancient sea, along with clay and sand. Over millions of years these sediments compacted, hardened, and turned into rock. The individual gold particles were then trapped within layers of solid rock. When the seas evaporated and the land shifted and collided, these layers of quartz and slate fractured and folded, producing hot fluids that migrated through the rocks and dissolved the gold. The gold was then deposited in quartz veins nearer the surface of the Earth.

Another theory proposes that gold was formed millions of years ago deep in the Earth. Through the movement of the Earth’s plates and volcanic activity, gold was dissolved in hot fluids and gases and then forced upwards by heat and pressure. Periodically, over millions of years, it was forced into cracks and fissures in the Earth’s mantle, often along with quartz or other minerals. As it moved nearer to the surface, the gold and quartz cooled into branching veins, much like the veins in our bodies. These veins can be so small that they are hardly visible or they can be many metres wide, and hundreds or thousands of metres long.

Most of the gold in Nova Scotia today is found in these veins, or lodes, of quartz. Some of these lodes run near the Earth’s surface, while others remain buried deep underground. If the lodes near the surface are exposed to the elements over thousands of years, erosion occurs and small chunks of quartz or flakes and nuggets of gold are washed away to new locations, usually into streams or rivers. This gold is called placer gold or alluvial gold. Placer gold is the form of gold most usually mined by individual prospectors, since placer deposits can easily be worked alone and do not require a lot of financial investment or heavy equipment.

Thousands of years of this weathering action on gold produces minuscule particles that aren’t heavy enough to settle on stream beds, so they continue to get washed along by the water until they reach the oceans. Surprisingly, the most significant reserve of gold on Earth today is in sea water, by some estimates as much as seven times the amount that has been mined since the beginning of history. Billions of tons of gold are dissolved in the world’s oceans at an estimated density of between five and 50 parts per trillion; the value of this gold is believed to be as much as $10 trillion. Recovering and processing the gold that is present in seawater is currently so expensive that it would not be worth the effort. However, research continues into methods that would make it profitable.
  

© 2013, Art Gallery of Nova Scotia. All Rights Reserved.

Photograph showing anticline and syncline folds in the rocks along the shoreline of Nova Scotia.

Photograph of folded sedimentary rocks forming well developed anticlines and synclines found along the Minas Basin shore. When continents or large land masses collide, the rock layers of the Earth’s crust are pushed up into mountains or folded and compressed into hills and valleys. These folds are called anticlines and synclines.

G. Prime, Nova Scotia Department of Natural Resources

Nova Scotia, CANADA
© 2013, Nova Scotia Department of Natural Resources. All Rights Reserved.


The Earth’s surface is not as stable as it seems. It is actually made up of huge plates of continental crust that are between five and 35 kilometres thick that are floating on oceanic crust. Scientists have discovered that, encircling the globe, there are a dozen large plates as well as a number of smaller ones. These plates move imperceptibly, at a rate of a few centimetres each year, and over the course of millions of years continents and oceans move and change shape. The plates pulling apart cause fractures or deep rifts in the Earth’s crust, both on land and under the sea, and plates colliding with each other form mountain ranges and new islands as the rock is forced upwards. We call this movement plate tectonics. The continents that existed millions of years ago look very different from the ones that are familiar to us today.

Even though we can’t feel it, these massive plates are still moving and colliding with each other, for example, in the Himalayas. Eventually, millions of years from now, continents will again be colliding with each other!
  
The Earth’s surface is not as stable as it seems. It is actually made up of huge plates of continental crust that are between five and 35 kilometres thick that are floating on oceanic crust. Scientists have discovered that, encircling the globe, there are a dozen large plates as well as a number of smaller ones. These plates move imperceptibly, at a rate of a few centimetres each year, and over the course of millions of years continents and oceans move and change shape. The plates pulling apart cause fractures or deep rifts in the Earth’s crust, both on land and under the sea, and plates colliding with each other form mountain ranges and new islands as the rock is forced upwards. We call this movement plate tectonics. The continents that existed millions of years ago look very different from the ones that are familiar to us today.

Even though we can’t feel it, these massive plates are still moving and colliding with each other, for example, in the Himalayas. Eventually, millions of years from now, continents will again be colliding with each other!
  

© 2013, Art Gallery of Nova Scotia. All Rights Reserved.

Illustration of the North American continent 290 million years ago.

All of the continents on Earth had collided and formed one giant supercontinent called Pangaea. Vast coal swamps formed on the equator, including over Nova Scotia.

Ron Blakey and Colorado Plateau Geosystems Inc.

© 2013, Ron Blakey and Colorado Plateau Geosystems Inc.. All Rights Reserved.


When all the continents collided about 290 million years ago, they formed the supercontinent Pangaea. After millions of years this supercontinent began to pull apart once again, creating new land masses. The land mass that we call Nova Scotia was originally part of the offshore marine environment and coastal areas of two different ancient continents, Gondwana (in the south) and Laurasia (in the north.) The place where these two land masses came together is called the Cobequid-Chedabucto Fault Zone. This largely invisible fault line splits mainland Nova Scotia into the Avalon Terrane to the northeast and the Meguma Terrane to the southwest. Most of Nova Scotia’s gold bearing lodes are located in the Meguma Terrane.

A Terrane is a region that is geologically distinct from its surroundings; it was originally associated with one tectonic plate but, because of continental movement over the course of millions of years, it has become attached to another plate with a different geological history. The rest of the land once associated with the Meguma Terrane may now be located along the western edge of Spain and Portugal or along the northwestern coast of Africa.
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When all the continents collided about 290 million years ago, they formed the supercontinent Pangaea. After millions of years this supercontinent began to pull apart once again, creating new land masses. The land mass that we call Nova Scotia was originally part of the offshore marine environment and coastal areas of two different ancient continents, Gondwana (in the south) and Laurasia (in the north.) The place where these two land masses came together is called the Cobequid-Chedabucto Fault Zone. This largely invisible fault line splits mainland Nova Scotia into the Avalon Terrane to the northeast and the Meguma Terrane to the southwest. Most of Nova Scotia’s gold bearing lodes are located in the Meguma Terrane.

A Terrane is a region that is geologically distinct from its surroundings; it was originally associated with one tectonic plate but, because of continental movement over the course of millions of years, it has become attached to another plate with a different geological history. The rest of the land once associated with the Meguma Terrane may now be located along the western edge of Spain and Portugal or along the northwestern coast of Africa.
  

© 2013, Art Gallery of Nova Scotia. All Rights Reserved.

Simplified illustration of anticline and syncline folds.

Folds that look like happy faces have the youngest rocks at the top and are called synclines. Folds that look like sad faces and have the oldest rocks at its core are called anticlines.

Art Gallery of Nova Scotia

© 2013, Art Gallery of Nova Scotia. All Rights Reserved.


When continents or large land masses collide, the rock layers of the Earth’s crust are pushed up into mountains or folded and compressed into hills and valleys. These folds are called anticlines and synclines. The anticline is an upward-facing fold where the rock layers are progressively older towards the centre of the fold; the syncline is the downward-facing fold that has younger rock layers at its centre.

In southern and eastern Nova Scotia, most of the rock layers are slate or quartzite. The weathering of the anticlines and synclines exposes the gold-bearing quartz to the surface.

All of the gold in Nova Scotia was originally deposited in the deep ocean basins off the coast of North Africa about 500 million years ago. The collision between North America and North Africa 385 million years ago caused the rocks to squeeze and fold. Spaces were created between the folds in the rocks, allowing fluids rich in gold to flow through. Almost all of the gold in present day Nova Scotia is now found in these folds in the rocks.
  
 
When continents or large land masses collide, the rock layers of the Earth’s crust are pushed up into mountains or folded and compressed into hills and valleys. These folds are called anticlines and synclines. The anticline is an upward-facing fold where the rock layers are progressively older towards the centre of the fold; the syncline is the downward-facing fold that has younger rock layers at its centre.

In southern and eastern Nova Scotia, most of the rock layers are slate or quartzite. The weathering of the anticlines and synclines exposes the gold-bearing quartz to the surface.

All of the gold in Nova Scotia was originally deposited in the deep ocean basins off the coast of North Africa about 500 million years ago. The collision between North America and North Africa 385 million years ago caused the rocks to squeeze and fold. Spaces were created between the folds in the rocks, allowing fluids rich in gold to flow through. Almost all of the gold in present day Nova Scotia is now found in these folds in the rocks.
  
 

© 2013, Art Gallery of Nova Scotia. All Rights Reserved.

Gold specimen from Nova Scotia containing 17.7 troy ounces.

Gold specimen of unknown Nova Scotian locality, containing 17.7 troy ounces of gold.

Photography by Roger Lloyd. Nova Scotia Museum.

Nova Scotia, CANADA
Nova Scotia Museum, 982GE0001.001 .
© 2013, Nova Scotia Museum. All Rights Reserved.


Weight   
Precious metals such as gold and silver, as well as gemstones, are measured differently than most other substances. Troy ounces were adopted as the official weight standard for coins in Britain in 1828. Troy ounces are subdivided into grains; one Troy ounce has 480 grains. We still use Troy ounces to weigh gold. Troy ounces are a little bit heavier than regular ounces.

Measurement: Quantity     
Troy ounces: 1 Troy ounce = 480 grains
Regular (avoirdupois) ounces equivalent: 1.09714 ounces
Metric system equivalent: 31.1034768 grams

Since 1870, just over 1 million Troy ounces of gold have been mined in Nova Scotia.


Purity
We use the term karats to talk about the relative purity of a particular gold object or gold specimen. The purest gold is 24 karats and is 99.9% gold. Anything less than this will have some other metal, such as silver or Read More
Weight   
Precious metals such as gold and silver, as well as gemstones, are measured differently than most other substances. Troy ounces were adopted as the official weight standard for coins in Britain in 1828. Troy ounces are subdivided into grains; one Troy ounce has 480 grains. We still use Troy ounces to weigh gold. Troy ounces are a little bit heavier than regular ounces.

Measurement: Quantity     
Troy ounces:
1 Troy ounce = 480 grains
Regular (avoirdupois) ounces equivalent: 1.09714 ounces
Metric system equivalent: 31.1034768 grams

Since 1870, just over 1 million Troy ounces of gold have been mined in Nova Scotia.


Purity
We use the term karats to talk about the relative purity of a particular gold object or gold specimen. The purest gold is 24 karats and is 99.9% gold. Anything less than this will have some other metal, such as silver or copper, mixed in with the gold, forming an alloy. Eighteen karat gold is 18 parts gold and six parts other metal, and 12 karat gold is actually less than half gold by volume.


Hardness
The Mohs scale of hardness measures the relative hardness of minerals by recording which minerals can scratch or be scratched by others. Although the formal scale was created in 1812, the general concept has been in use for over two thousand years. Diamonds are the hardest known minerals – nothing can scratch a diamond – so diamonds were given a value of 10; everything else is softer and so has a lower number. On the Mohs scale, gold has a value of about 2.5. This is around the same hardness as a human fingernail. Quartz, which holds much of the gold found in Nova Scotia, has a hardness value of 7. Pyrite or fool’s gold, which is often mistaken for gold, measures between 6 and 6.5 on the Mohs scale. Hardness can also be measured with a sclerometer. This method was invented in 1896 and involves measuring the width of a scratch on a mineral made by a diamond, using a microscope.
     

© 2013, Art Gallery of Nova Scotia. All Rights Reserved.

Detail photograph of a pyrite specimen.

Close-up of a pyrite specimen from Beaverbank, Nova Scotia. Pyrite is shiny and yellow and people so often confuse it for gold it is known as “fool’s gold”. Pyrite is brassy yellow and often forms in cubes.

Photography by Roger Lloyd. Nova Scotia Museum.
Fred Walsh, Prospector.

Beaverbank, Nova Scotia, CANADA
© 2013, Fred Walsh. All Rights Reserved.


Pyrite, an iron sulfide, is also called ‘fool’s gold’ because it has often been mistaken for gold by inexperienced miners. It can be a similar colour, but is often more brassy or silvery. Colour is really the only characteristic that pyrite shares with gold. It is a much harder mineral than gold. If pyrite is hammered it will crumble, while gold is extremely malleable in its pure form and can be shaped and hammered easily without cracking or crumbling. Occasionally real gold can be found within pyrite, which may account for some of the confusion.
  
Pyrite, an iron sulfide, is also called ‘fool’s gold’ because it has often been mistaken for gold by inexperienced miners. It can be a similar colour, but is often more brassy or silvery. Colour is really the only characteristic that pyrite shares with gold. It is a much harder mineral than gold. If pyrite is hammered it will crumble, while gold is extremely malleable in its pure form and can be shaped and hammered easily without cracking or crumbling. Occasionally real gold can be found within pyrite, which may account for some of the confusion.
  

© 2013, Art Gallery of Nova Scotia. All Rights Reserved.

Humans have made many attempts to create valuable minerals – so-called noble metals, chiefly gold and silver – from base metals such as lead, through the process of transmutation. For many thousands of years, this was one of the main aims of the practice of alchemy. Alchemists thought that all metals were made up of different amounts of sulfur and mercury, so they thought they could turn any metal into gold by varying the proportions of each of these two metals. Gold has always been valuable, so they were trying to find an easier way to get rich. Gold’s unchanging properties also represented eternity. Alchemists believed that if they could transmute lead into gold, they would have found the secret to eternal life. They tried many different formulas and many different processes. Even though the theory was wrong and they were never successful, the methods of the alchemists formed the basis for modern chemistry.
  
Humans have made many attempts to create valuable minerals – so-called noble metals, chiefly gold and silver – from base metals such as lead, through the process of transmutation. For many thousands of years, this was one of the main aims of the practice of alchemy. Alchemists thought that all metals were made up of different amounts of sulfur and mercury, so they thought they could turn any metal into gold by varying the proportions of each of these two metals. Gold has always been valuable, so they were trying to find an easier way to get rich. Gold’s unchanging properties also represented eternity. Alchemists believed that if they could transmute lead into gold, they would have found the secret to eternal life. They tried many different formulas and many different processes. Even though the theory was wrong and they were never successful, the methods of the alchemists formed the basis for modern chemistry.
  

© 2013, Art Gallery of Nova Scotia. All Rights Reserved.

The alchemists would be surprised to learn that certain microbes can change the nature of gold. An extremophile is a microorganism that lives in extreme environments, places where most life on earth could not survive. In the 1990s, microbiologists discovered that some microorganisms get energy from breathing in or ingesting dissolved particles of metals that are toxic to humans. Researchers wondered if they could find microbes that “ate” gold, and explored undersea hydrothermal vents and hot springs, where dissolved gold is more likely to be found. Back in their laboratories, the microbes they had collected in these locations were able to convert gold from a dissolved form into an insoluble metallic form, although the particles were still very tiny. Researchers estimate that it would take over a million microbes to produce just one gram of gold.
  
The alchemists would be surprised to learn that certain microbes can change the nature of gold. An extremophile is a microorganism that lives in extreme environments, places where most life on earth could not survive. In the 1990s, microbiologists discovered that some microorganisms get energy from breathing in or ingesting dissolved particles of metals that are toxic to humans. Researchers wondered if they could find microbes that “ate” gold, and explored undersea hydrothermal vents and hot springs, where dissolved gold is more likely to be found. Back in their laboratories, the microbes they had collected in these locations were able to convert gold from a dissolved form into an insoluble metallic form, although the particles were still very tiny. Researchers estimate that it would take over a million microbes to produce just one gram of gold.
  

© 2013, Art Gallery of Nova Scotia. All Rights Reserved.

1. Read more about the Mohs scale and gather a selection of minerals that look different from each other. Try to scratch each mineral using each of the other rocks and record your findings.
    a. Can you use the Mohs scale to help you identify them?
    b. Can you create your own hardness scale?

2. Create a crossword puzzle for your classmates using at least 12 words and clues from this section on The Geology of Gold.

3. Using layers of folded cloth, clay, or paper, create and label a model of anticlines and synclines.

4. Research plate tectonics, and learn about the direction in which the various plates are moving. Find an image of what the world looked like two million years ago and compare it to the present. Draw a map of the way you think the world might look in another 3 million years. Are there new continents? Oceans? Mountain ranges? What would you name them?
  
1. Read more about the Mohs scale and gather a selection of minerals that look different from each other. Try to scratch each mineral using each of the other rocks and record your findings.
    a. Can you use the Mohs scale to help you identify them?
    b. Can you create your own hardness scale?

2. Create a crossword puzzle for your classmates using at least 12 words and clues from this section on The Geology of Gold.

3. Using layers of folded cloth, clay, or paper, create and label a model of anticlines and synclines.

4. Research plate tectonics, and learn about the direction in which the various plates are moving. Find an image of what the world looked like two million years ago and compare it to the present. Draw a map of the way you think the world might look in another 3 million years. Are there new continents? Oceans? Mountain ranges? What would you name them?
  

© 2013, Art Gallery of Nova Scotia. All Rights Reserved.

Learning Objectives

1. Investigate rocks and minerals and record questions and observations.
    (Science, Grade 7)

2. Classify rocks and minerals by creating a chart or diagram that illustrates the classification scheme.
    (Science, Grade 7)


3. Describe natural phenomena that cause rapid and significant changes.
    (Science, Grade 7)


4. Demonstrate a sensitivity towards the natural and built environment through their art work.
    (Visual Arts, Grades 7-12)

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