Gold Properties in 11 Parts: From Physical to Chemical, to its Origins, Alloys and Assaying – All You Need to Know

This is an extensive overview in 11 parts about the properties of gold – from physical and chemical properties to its origins, alloys and assaying; also: gold’s attractiveness, biological role, formation in the universe and occurance on earth, rarity, and authentitiy checks.

Jump right to the article below.

Infographic about gold properties:

Infographic about Gold properites to its origins, alloys and assaying.
Infographic about Gold properites to its origins, alloys and assaying.

Introduction

Gold, a metal that has shaped human history, continues to play a pivotal role in various sectors of our modern world. Its significance isn’t just rooted in its economic value, but also in its diverse applications and intriguing gold properties.

Women wearing gold jewelry.
Women wearing gold jewelry.

In this guide, we’ll delve into multiple facets of gold, including:

  • Its distinct physical and chemical properties that differentiate it from other elements.
  • Gold’s presence and role in the vast expanse of the universe.
  • Theories and facts surrounding its origins on Earth.
  • The biological significance of gold, a topic that might surprise many.
  • Methods and techniques like assaying, crucial for determining gold’s purity and authenticity.

With each section, we aim to provide a comprehensive understanding of gold’s multifaceted nature. Whether you’re directly involved in the gold trade, an academic, or someone keen on expanding their knowledge, this guide promises insights that will enrich your perspective on this remarkable metal.

Some of gold’s properties:

Category Explanation
Physical and Chemical Properties Gold is the most malleable of all metals; a single gram can be beaten into a sheet of 1 square meter.
Gold’s Historical Significance The Lydians, an ancient civilization in modern-day Turkey, are credited with minting the first gold coins around 2,500 years ago.
Origins of Gold on Earth Over 80% of the Earth’s gold is still buried underground and remains undiscovered.
Biological Significance of Gold The human body contains about 0.2 milligrams of gold, mostly in the bloodstream.
Gold’s Purity The purity of gold is measured in karats, with 24 karats being 100% pure gold.
Gold’s Role in Technology Gold’s high conductivity makes it indispensable in advanced electronics, including GPS units, TVs, and cell phones.

Let’s start with the reasons for gold’s attractiveness.

Part 1: Reasons for Gold’s Attractiveness

Gold is considered attractive for a variety of reasons, including its physical properties, cultural significance, and investment potential.

Attractiveness of gold.
Attractiveness of gold.

Gold Properties

Gold is a dense, soft, and malleable metal that is highly attractive, bright, and shiny.

unique gold properties include:

  • Resistance to tarnish and corrosion.
  • High electrical conductivity.
  • Malleability, allowing it to be shaped into intricate designs.

These properties have led to its diverse applications in:

  • Electronics: Gold connectors ensure efficient performance in devices like smartphones.
  • Medicine: Gold isotopes are used in treatments for certain types of cancer.
  • Aerospace: Satellites use gold-coated films to protect against harmful radiation.

Further, it is easy to work with and can be found in its natural form in rivers.

Cultural Significance

Gold has been revered within the mythologies, legends, and histories of numerous cultures around the globe throughout history. It has been used in ancient healing traditions and has many mysterious, mystical, or metaphysical associations with the sun, various deities, and magical powers. Gold is also associated with success and wealth, making it a symbol of status and prestige.

Old Plum by Kano Sansetsu, Japanese painting with gold foil from 1646
Old Plum by Kano Sansetsu, Japanese painting with gold foil from 1646 (The Met).

Civilizations, from the Pharaohs of Egypt to the emperors of Rome, have coveted this precious metal. Its rich history is evident in:

  • Ancient coins, such as the Roman aureus, which showcased the empire’s affluence.
  • Historical texts and scriptures that frequently mention its unparalleled value.

In fact, during the Byzantine Empire, solid gold coins called “solidus” were in circulation for over 700 years, attesting to gold’s enduring appeal.

Gridle with coins and medallions from the Byzantine Empire, ca. 583
Gridle with coins and medallions from the Byzantine Empire, ca. 583 (The Met).

Investment potential

Gold has been used as a store of value and a medium of exchange for centuries.

It does not get used up or consumed like other commodities, imbuing the precious metal with a sense of everlasting value.

From an investment perspective, gold is attractive because of its potential to remain strong in difficult financial environments and to hedge against inflationary pressures. During times of fear and uncertainty, gold has historically been a go-to investment for many investors.

What are the gold properities?

They can be divied into physical and chemical properites.

Part 2: Physical Properties of Gold

This table provides a focused overview of the physical and chemical properties of gold:

Property Description
Atomic Number 79
Density 19.3 grams per cubic centimeter at 20°C
Color metallic yellow
Melting Point 1,064°C (1,947°F)
Boiling Point 2,800°C (5,072°F)
Malleability One of the most malleable metals; can be beaten into thin sheets
Ductility One of the most ductile metals; an be drawn into thin wires
Conductivity Excellent conductor of electricity
Inertnet Highly resistant to tarnish and corrosion

The Unique Yellow Color of Gold

Gold, a chemical element symbolized by Au on the periodic table with an atomic number of 79. Is well-known for its distinctive yellow color. This color is due to the absorption of light by the metal’s electrons, which results in a specific range of light being reflected that we perceive as gold’s characteristic hue.

The color of gold can also change depending on the type of alloy it forms. For instance:

  • Mixing gold with copper produces a redder alloy.
  • Combining it with silver or palladium results in a whiter shade.

However, the unique yellow color of pure gold remains a defining characteristic of this precious metal.

Different colors of gold, silver and copper alloys
Different colors of gold, silver and copper alloys (wikipedia/ Metallos CC BY-SA 3.0).

High Density and Its Implications

Another key physical property of gold is its high density. Gold has a density of approximately 19.3 grams per cubic centimeter, making it one of the densest elements known to man. The densest object, osmium, is not much denser with 22.588 g/m3. This high density means that even a small amount of gold can be quite heavy. For example, a gold bar the size of a common brick would weigh about 12.4 kilograms (27.3 pounds). A similar density has tungsten, at 19.25 g/cm3.

The high density of gold has practical implications. It allows for easy separation of gold from other materials in gold panning and other mining activities. The high density also means that gold sinks in water, which is why it often accumulates at the bottom of rivers and streams.

Malleability and Ductility of Gold

Check out the video: Malleability of gold:

Gold is renowned for its malleability and ductility.

  • Malleability refers to the ability of a substance to be hammered or rolled into thin sheets without breaking. Gold is the most malleable of all metals. A single ounce of gold can be beaten into a sheet measuring roughly 5 meters on a side.
  • Ductility, on the other hand, is the ability of a substance to be drawn into thin wires. Again, gold is a champion in this regard. A single gram of gold can be drawn into a wire over 2 kilometers long.
Malleability of gold: a gold nugget of 5mm in size is hammered into a gold foil of 0.5m2
Malleability of gold: a gold nugget of 5mm in size is hammered into a gold foil of 0.5m2 (wikipedia/ PHGCOM CC-BY SA 3.0).

These properties have made gold invaluable in many applications, especially in jewelry making and electronics.

Melting and Boiling Points

Gold has a relatively high melting point of 1064.18 degrees Celsius (1947.52 degrees Fahrenheit). The boiling point of gold is 2856 degrees Celsius (5173 degrees Fahrenheit)

Comparing Gold’s Physical Properties with Other Metals

When compared to other metals, gold’s physical properties stand out. Its unique yellow color, high density, malleability, and ductility set it apart from most other elements.

For example:

  • While silver and copper are also highly malleable and ductile, they lack gold’s resistance to tarnish and corrosion.
  • Platinum is as resistant to corrosion as gold, but it is much less malleable and ductile.

In conclusion, the physical properties of gold, including its color, density, malleability, and ductility, contribute to its status as a highly valuable and sought-after metal. These properties not only make gold aesthetically pleasing but also highly useful in a variety of applications.

Part 3: Chemical Properties of Gold

Gold’s Inertness

One of the defining chemical properties of gold is its inertness. Gold is considered a noble metal, meaning it is resistant to corrosion and oxidation in moist air, unlike many other elements. This property is due to the stability of the gold atom’s electron configuration, which prevents it from readily forming compounds with other elements.

The inertness of gold has significant implications. For instance:

  • Gold artifacts that are thousands of years old can be found in near-pristine condition today.
  • This property also makes gold ideal for a variety of applications, such as in jewelry making and electronics, where resistance to corrosion is essential.

Solubility of Gold

Despite its inertness, gold does have some solubility under specific conditions. Most notably, gold can dissolve in a mixture of nitric acid and hydrochloric acid, known as aqua regia (Latin for royal water). This mixture creates a chemical environment capable of breaking down gold’s stable electron configuration, leading to its dissolution.

Dissolution of a one gram gold bar in Aqua Regia.
Dissolution of a one gram gold bar in Aqua Regia (wikipedia/ Daniel Grohmann CC BY-SA 3.0).

Interestingly, the ability of aqua regia to dissolve gold was historically used as a method to authenticate gold items. If an item suspected to be gold did not dissolve in aqua regia, it was confirmed to be genuine gold.

Gold’s Resistance to Tarnish and Corrosion

Gold’s resistance to tarnish and corrosion is another important chemical property. Unlike many other metals, gold does not react with oxygen in the air to form a dull layer on its surface. This property, combined with its inertness, contributes to gold’s lasting shine and color.

For example, consider the difference between silver and gold:

  • Silver tarnishes over time due to a reaction with sulfur compounds in the air, leading to a black layer of silver sulfide on its surface.
  • In contrast, gold remains shiny and untarnished, even over long periods.

Gold’s Chemical Properties and Their Impact on Its Use in Electronics

The chemical properties of gold, particularly its inertness and resistance to corrosion, make it highly valuable in the electronics industry. Gold is an excellent conductor of electricity and does not corrode or tarnish, making it ideal for use in precision electronic equipment.

Its reliability and resistance to corrosion ensure that electronic devices function efficiently and reliably over time. In fact, NASA uses gold in various components of its spacecraft due to these properties.

Gold’s Chemical Properties and Their Impact on Its Use in Dentistry

Gold’s chemical properties also make it valuable in dentistry. Its inertness means it does not react with chemicals in the mouth or cause an allergic reaction, making it safe for use in fillings, crowns, and bridges.

gold in dentistry :artifical crown and bridge work from 1889
gold in dentistry :artifical crown and bridge work from 1889 (flickr/ Internet Book Archive).

Moreover, gold’s malleability and ductility, combined with its chemical stability, allow it to be shaped into precise forms that can withstand the harsh environment of the mouth. As a result, gold has been used in dentistry for thousands of years and continues to be used today. In fact, it’s estimated that about 13% of gold’s annual demand comes from the dental industry.

Part 4: Biological Role of Gold

Gold does not have a known biological role and is considered non-toxic to humans. However, certain gold compounds, especially gold salts used in medical treatments, can have side effects.

Gold in the Human Body

Gold is not considered an essential mineral for the human body; it doesn’t play a known role in any bodily functions.

The human body does contain trace amounts of gold. However, the quantity is minuscule.

Most of the gold in the human body is found in the bloodstream. However, if you were to extract all the gold from an average-sized person’s body, weighting 70kg, you’d get a tiny speck—just about 0.2 milligrams.

To put this in perspective, you would need to harvest the gold from around 40,000 people to collect enough gold to make an 8-gram (0.28 ounces) gold ring.

thousands of golden people, dystopian image
thousands of golden people, dystopian image

Gold in Medical Applications

While gold nanoparticles have been used in various medical applications, such as bio-imaging, drug delivery, and diagnostics, their use is not directly related to any biological function of gold itself.

Gold compounds have been used for anti-inflammatory and anti-bacterial purposes, but these applications are based on the chemical properties of the compounds rather than the biological role of gold.

Part 5: Gold Formation in the Universe

The formation of gold in the universe has been the subject of scientific investigation and theories.

Gold in space, a creative visualization.
Gold in space, a creative visualization.

Here are three of the theories proposed on the origins of gold in space:

Supernova nucleosynthesis

  • When massive stars reach the end of their life cycle, they explode in a cataclysmic event called a supernova.
  • During a supernova, the intense heat and pressure can create the conditions necessary for the formation of heavy elements like gold (rapid neutron capture).
  • The explosion disperses these elements into space, where they can eventually become part of new star systems and planetary bodies.

Also check out the video about the origins of gold:

Neutron Star Collisions

  • Another theory gaining traction is that gold can form through the collision of two neutron stars.
  • When two neutron stars merge, the extreme conditions generate intense gravitational forces and high-energy reactions.
  • These collisions are believed to produce heavy elements, including gold, which are then ejected into space. This was observed in 2017.

Nuclear Fusion in Stars

  • Gold is not formed through regular nuclear fusion in stars.
  • Early stars primarily produced lighter elements like carbon, nitrogen, and oxygen through fusion reactions.
  • As these stars exhausted their lighter elements, they began fusing heavier elements, eventually leading to the formation of gold.

It is important to note that these theories are not mutually exclusive, and multiple processes may contribute to the formation of gold in the universe. Further research and observations, such as those conducted by the Laser Interferometer Gravitational-Wave Observatory (LIGO), have provided valuable insights into the origin of gold and other heavy elements.

Overall, the formation of gold in the universe is a complex process involving stellar events and nuclear reactions. The collision of stars, supernovae, and neutron star mergers are believed to be key contributors to the creation of this precious metal.

The Presence of Gold on Other Planets

The Nasa LCROSS mision detected gold on the moon in 2009.
The Nasa LCROSS mision detected gold on the moon in 2009 (NASA).
  • Mars: The presence of water and certain minerals on Mars suggests that gold could exist on the planet. However, the presence of gold on Mars has not been confirmed yet, and more research and study is needed to confirm its existence. check out the article about gold on mars.
  • Moon: The NASA LCROSS mission discovered gold on the moon in 2009. This was accomplished by an aircraft that smashed into the moon. A second, in orbit, equipped with a mass spectrometer analysed the debris and dust from the impact. It detected several chemicals, among them gold. check out the article about gold on the moon.
  • Other Planets: it is safe to assume that gold is present on other planets – only the quantity must still be determined. check out the article about gold in the sun.

The Significance of Gold in the Study of the Universe

The study of gold and its formation processes provides valuable insights into the workings of the universe. By understanding how gold is formed, scientists can gain insights into the life cycle of stars, the processes that occur during supernova explosions, and the conditions during the early universe. Furthermore, the presence of gold in meteorites can provide clues about the formation and evolution of the solar system.

Part 6: Gold on Earth: Theories and Facts

Erupting volcanoe, bringing gold to the surface of the earth.
Erupting volcanoe, bringing gold to the surface of the earth.

Theories About the Formation of Gold on Earth

The formation of gold on Earth is a subject of extensive scientific research. There are several theories about how gold is formed on our planet.

Volcanic Activity

Gold is believed to be formed from magma chambers under volcanoes. These chambers are extremely hot, with temperatures of around 800 degrees Celsius (1,472 degrees Fahrenheit) or more.

When a volcano erupts, a significant release of pressure occurs in the magma chamber. The gases released include steam, carbon dioxide, sulfur dioxide, hydrogen, hydrochloric acid, and hydrogen sulfide. Chlorine and gold from the magma combine to form compounds such as hydrogen gold chloride (HAuCl2). These compounds are drawn out of the magma chamber dissolved in superheated steam and deposited in fractures in surrounding rocks. This process is akin to opening a soda pop bottle, where the release of pressure leads to the release of carbon dioxide gas.

Hydrothermal Alteration

Another theory posits that gold is formed through a process called hydrothermal alteration
This process involves superheated steam and other gases from magma chambers chemically wearing down the surrounding rock, leading to the formation of gold. This process is similar to the natural weathering and erosion processes, but on a much more intense scale due to the high temperatures and pressures involved.

Superheated Water

The current theory on gold formation is that superheated water carries the metals in solution.

The water flows below ground through fissures and into areas less hot so that the solution cools. When it cools, the metal (in this case gold) precipitates out of solution and covers the wall of the fissure or grains of rock within the area through which the water is flowing. This process is similar to how minerals are deposited in caves, where water carrying dissolved minerals drips from the ceiling and evaporates, leaving the minerals behind to form stalactites and stalagmites.

Meteorites

meteroide shower at the night sky
meteroide shower at the night sky.

The gold concentration of the earth should have left Earth’s outer layer devoid of gold. However, the Earth’s silicate mantle is relatively rich in gold and other precious metals. Some experts believe that this surplus of gold came from a massive meteorite storm that struck Earth after its core was established, 200 million years of the planets inception. This means that the meteorites’ gold only enriched the mantle, without sinking deeper inside. This research theory was published in 2011 in the journal Nature.

Part 7: The Rarity of Gold

Embarking on the quest for gold.
Embarking on the quest for gold.

Understanding the Rarity of Gold

Gold, a lustrous yellow precious metal, has been a symbol of wealth and status in many cultures for thousands of years. Its rarity is one of the key reasons for its high value. But what exactly makes gold so rare?

  1. Geological availability: Gold is not evenly distributed around the world. It is found in certain geological formations known as gold-bearing veins. These veins are often located deep underground, making them difficult to access. According to the U.S. Geological Survey, only about 244,000 metric tons of gold has been extracted to date. The world production of gold is 1.5 million kg. This is a cube with 4.3 meters on per side. If every single ounce of this gold were placed next to each other, the resulting cube of pure gold would only measure around 23 meters on each side.
  2. Extraction difficulty and refining costs: Gold cannot be manufactured or synthetically produced. It must be extracted from the earth, a process that is expensive, time-consuming, and often dangerous.
  3. Refining process: After extraction, gold must be refined to remove impurities. This process is complex and requires a high level of expertise.
  4. Environmental Impact: Mining for gold often has a significant environmental impact, including deforestation, soil erosion, and contamination of water sources. This impact can limit where and how much gold can be mined.

Comparing Gold’s Rarity with Other Precious Metals

Table of Crystal Abundance of gold, platinum and silver.
Table of Crystal Abundance of gold, platinum and silver.

When compared to other precious metals, gold’s rarity becomes even more apparent:

  1. Gold vs. Silver: The crustal abundance of gold is 0.004 parts per million (ppm), while silver is 0.075 ppm. This means that there is almost 19 times more silver than gold in the earth’s crust.
  2. Gold vs. Platinum: Platinum is even rarer than gold, with a crustal abundance of 0.005 ppm. However, because platinum is more difficult to extract and refine than gold, it is often more expensive. Read more on the website of the Royal Mint.
  3. Other metals: nickel and copper are much more common to find. Nickel is at 84 and copper at 60 ppm. That is 21.000 and 15.000, resp., times more common than gold!

Demand

The demand for gold, particularly in the jewelry industry, has historically outstripped supply, further contributing to its rarity and value

The Future of Gold: Considering Its Rarity

The future availability of gold is a topic of much debate among experts. Some believe that we have already reached ‘peak gold’, the point at which the maximum rate of global gold extraction is reached. After this point, the rate of extraction is expected to decline, making gold even rarer.

However, others argue that advances in mining technology and the potential for space mining could increase the supply of gold in the future. Only time will tell which of these predictions will come true.

Part 8: Karat, Fineness, and Troy Ounce

Gold bar of one fine ounce of 999.9 gold.
Gold bar of one troy ounce of 999.9 gold (pixabay/ StockSnap).

The Origin and Meaning of Karat

In the context of gold, karat is a unit of measurement used to express the proportion of gold in a piece of jewelry or any other item made of gold. It is denoted by the symbol ‘k’ in the United States. In Many other countries it is written as carat and abbreviated as c.

Pure gold is defined as 24 karat, meaning it is 100% gold (to be exact: it is at least 99.9% of gold, as refining 100% pure gold is impossible); see also 999 gold. However, because pure gold is too soft for most uses, it is often mixed with other metals to increase its hardness and durability. For example, a 18K gold piece consists of 75% gold and 25% other metals. Similarly, 14K gold contains 58.3% gold, and 10K gold contains 41.7% gold.

The term karat has its roots in the ancient Mediterranean. It was derived from the word ‘keration’ in Greek and ‘qirat’ in Arabic, both meaning ‘fruit of the carob tree’. Carob seeds were known for their uniformity in weight and were used as counterweights in balance scales to measure precious metals. The term karat was later adopted in the West and has been used to measure the purity of gold.

What Does Fineness Mean?

Ring with hallmark and fineness stamp of 583 gold
Ring with hallmark and fineness stamp of 583 gold (wikipedia/ Star61 BB-BY SA 3.0).

Fineness refers to the purity of precious metals, expressed in parts per thousand. For instance, the fineness of 24K gold is 999.9, implying that out of 1,000 parts, 999.9 are pure gold. This measurement is often stamped on gold items as a hallmark, providing a guarantee of the precious metal content. 999.9 is a standard fineness for gold as investment (coins or bars).

The History and Meaning of Troy Ounce

The troy ounce is a specific measure of gold and other precious metals. It is based on the troy ounce, which is equal to 31.1034768 grams. A troy ounce refers to a troy ounce of pure gold content in a gold bar, computed as fineness multiplied by gross weight. This measure is often used in the trading of gold and other precious metals. See also: how many grams in one ounce of gold?.

The term “troy” is derived from the French town of Troyes, which was a major trading city in the Middle Ages. The troy ounce was part of the duodecimal system of weights used in England and other countries influenced by English custom. This system was based on the pennyweight, which was equivalent to 24 grains or 1/20 of a troy ounce.

Measuring Gold Purity with Karat, Fineness, and Troy Ounce

Karat, fineness, and troy ounce are all used to measure the purity of gold, each offering a different perspective. Karat measures the proportion of gold in an alloy, fineness measures the purity of the gold in parts per thousand, and the troy ounce refers to the pure gold content in a gold bar.

The Impact of Gold Purity on Its Value

The purity of gold, as measured by its karat, fineness, or troy ounce, has a significant impact on its value. The purer the gold, the higher its value. However, because pure gold is soft and not suitable for many applications, gold of lower karat, which is mixed with other metals for strength, is often more desirable for things like jewelry.

The Role of Gold Purity in Jewelry Making

In jewelry making, the purity of gold plays a crucial role in determining the piece’s durability, color, and value. Higher karat gold is softer and more prone to scratching, while lower karat gold is harder and more durable. The type and proportion of other metals mixed with gold also affect the color of the final product. For instance, mixing copper with gold results in a reddish color, creating what is known as rose gold. Similarly, adding silver or palladium can result in white gold.

Key Facts about fineness and karat:

Measurement/Type Description
31.1034768 grams Weight of a troy ounce
24 karat The measurement for pure gold.
999.9 gold The fineness of pure gold.
Fine ounce A troy ounce of pure gold in a gold bar.
750 gold The gold content in a 18K gold piece.
585 gold
The gold content in a 14K gold piece.
417 gold
The gold content in a 10K gold piece.

This table provides a concise overview of various measurements and descriptions related to gold.

Part 9: Alloys and Compounds of Gold

Gold is a versatile metal that forms various alloys and compounds, each with unique properties and applications.

Common metals used for gold alloys: silver, copper, nickel, iron, aluminium and others.
Common metals used for gold alloys: silver, copper, nickel, iron, aluminium and others (wikipedia/ Mauro Cateb CC BY-SA 3.0).

Gold-Silver Alloy (Electrum)

Electrum is a naturally occurring alloy of gold and silver. It has been used since ancient times due to its increased hardness compared to pure gold.

  • Composition: Varies, but typically around 50-60% gold and 40-50% silver.
  • Uses: Used in ancient coinage, jewelry, and decorative items.
  • Properties: Harder than pure gold, with a color varying from pale yellow to silvery depending on the silver content.

Gold-Aluminium Alloy

Gold-aluminium alloys are less common and are typically used for specialized purposes.

  • Composition: Around 79% gold and 21% aluminium for purple gold.
  • Uses: Due to its brittleness, it’s often used as a “gem” in conventional jewelry rather than by itself.
  • Properties: Purple gold is more brittle than other gold alloys.

Gold Chloride

Gold chloride is a compound of gold and chlorine. It’s a very important gold compound used in a number of industrial applications.

  • Composition: One atom of gold and one or more atoms of chlorine.
  • Uses: Used in photography for toning the silver image.
  • Properties: Gold(III) chloride is very hygroscopic and highly soluble in water as well as ethanol.

Gold Cyanide

Gold cyanide is used in mining for gold extraction.

  • Composition: One atom of gold and one molecule of cyanide.
  • Uses: Primarily for gold mining, and also in electroplating.
  • Properties: Highly toxic.

Check out the video of refining gold from alloy:

Colored Gold

Gold can be alloyed with various other metals to produce different colors.

This table provides a clear distinction between the type of gold, its composition, and a brief description:

Type of Gold Composition Description
White Gold 90% gold, 10% nickel (or other white metals) An alloy of gold and at least one white metal, commonly nickel, silver, or palladium.
Yellow Gold 75% gold, 12.5% copper, 12.5% silver The common alloy for 18K yellow gold.
Rose, Red, Pink Gold 75% gold, 25% copper (varies based on red coloration intensity) The difference between these types is the copper content. The higher the copper content, the stronger the red coloration.
Green Gold 75% gold, 15% silver, 6% copper, 4% cadmium Known to the ancient Persians as electrum, a naturally occurring alloy of silver and gold. The specific alloy yields a dark-green color.
Grey Gold Gold, palladium (or silver, manganese, copper in cheaper alternatives) Alloys are usually made from gold and palladium. A cheaper alternative which doesn’t use palladium is made by adding specific ratios of other metals.
Blue Gold 46% gold, 54% indium An alloy of gold and either gallium or indium. The specific compound formed is AuIn2.
Black Gold Gold with sulfur- and oxygen-containing compounds, amorphous carbon, or chromium/cobalt (varies by method) Black-colored gold can be produced by various methods such as patination, plasma-assisted chemical vapor deposition, or controlled oxidation.

These alloys and compounds of gold not only enhance the versatility of gold but also add to its aesthetic appeal in various applications, especially in jewelry making.

Part 10: Gold Assaying – Determine the Purity of Gold

Smiling African Man with gold on his face.
Smiling African Man with gold on his face.

Understanding Gold Assaying

Gold assaying is the systematic process used to determine the content and purity of gold within an object or ore. This age-old procedure ensures that gold items, from jewelry to coins, meet established purity standards.

Historically, gold has been a universal symbol of wealth and prestige. Its value is intrinsically tied to its purity. For instance, while a 24K gold item is 99.99% pure, a 22K item has slightly less gold content. Assaying provides a precise answer to the purity level, ensuring authenticity and value.

Check out the Video about analysis of high purity gold by the fire assay method:

https://www.youtube.com/watch?v=BDgvaDwXaf8

The Significance of Assaying in Today’s Gold Market

In today’s bustling gold market, assaying stands as a foundational pillar. It’s not just about determining purity; it’s about establishing trust and ensuring value in every transaction.

  • For Buyers: Assaying guarantees they’re receiving the gold quality they paid for.
  • For Sellers: It confirms that their gold products meet market standards, ensuring optimal market prices.

To illustrate, consider the global gold market where a 0.01% difference in purity can translate to hundreds or even thousands of dollars in price variations. Assaying plays a pivotal role in setting these prices.

Key Components in Gold Assaying

  1. Dry Assaying Method: An ancient technique involving the heating of gold to segregate it from other elements. It’s revered for its accuracy.
  2. Wet Assaying Method: A more intricate method that employs chemical solutions to ascertain gold purity. Often used for complex samples.
  3. Fluxes and Reagents: Essential chemicals aiding in the separation of gold from impurities.
  4. Oxidizing and Reducing Agents: Chemicals that influence oxygen levels during the assay, directly impacting results.
  5. Desulphurizing and Collecting Agents: Specifically used to extract sulfur and accumulate gold particles.

For a practical perspective, if a jeweler aims to validate the purity of a gold necklace before acquisition, they’d employ assaying techniques. The outcome, whether it’s 18K, 22K, or 24K, would then dictate the purchase price.

Non-Destructve Assaying

Fire assaying requires the gold to be melted down, other methods need a piece of the gold for analysis. If the goal is to authenticate the gold without causing damage, there are several ways to accomplish non-destructive assaying:

  • Spectrophotometry: a spectrometer analyses the light reflected by the sample, to determine its spectral reflectance curve (SRC). It is sensitive enough to tell the difference between solid and plated gold.
  • Ultrasonic testing measures the consistency of the material being tested.
  • Thermal conductivity testing checks how well the metal conducts thermal energy.
  • Energy-dispersive X-ray spectroscopy (EDS): this can measure the chemical and physical characteristics of the sample

Check out the video about ultrasonic testing of gold:

Assaying Through the Ages

While the core principles of assaying remain unchanged, the methodologies have seen significant advancements. Today’s assayers leverage state-of-the-art tools and advanced chemical solutions, ensuring unparalleled precision. This evolution is paramount in the contemporary gold market, where even minute discrepancies in purity can have substantial financial implications.

In 2020 alone, the global gold market was valued at approximately $200 billion. With such high stakes, the role of accurate assaying becomes even more critical.

In wrapping up, gold assaying seamlessly merges ancient traditions with modern-day technologies. It’s the gold standard (pun intended) in verifying purity, making it indispensable in the world of gold trade and commerce.

Part 11: Checking the Authenticity of Gold

gold rings: checking for authenticity.
gold rings: checking for authenticity.

Ensuring the authenticity of your gold items is crucial, not just for peace of mind but also for its true value.

Understanding Gold’s Authenticity Markings

One of the primary ways to determine the authenticity of gold is through its hallmarks. These are small imprints or stamps found on gold items, indicating their purity. For instance, a hallmark reading “24K” signifies pure gold, while “18K” indicates 75% gold content.

However, hallmarks can be misleading. Some fake gold items might carry genuine-looking hallmarks. On the other hand, older genuine gold pieces might lack hallmarks altogether. It’s essential to understand that while hallmarks can be a good starting point, they shouldn’t be the sole determinant of authenticity.

Simple At-Home Tests for Gold Authenticity

There are several straightforward tests you can conduct at home to gauge the authenticity of your gold:

  • The Water Test: Real gold has a high density. If you drop a gold item into a container of water, it should sink. Fake gold or gold alloys will likely float or hover above the bottom.
  • The Vinegar Test: By placing your gold item into a cup of white vinegar, genuine gold will retain its color, while fake gold will show signs of discoloration.
  • The Magnet Test: Gold is not magnetic. Holding a magnet close to the gold item, if it’s attracted, it’s likely not pure gold. However, remember that non-magnetic metals can also be added to fake gold.

Check out the video about testing gold at home:

Observing Physical Characteristics of Gold

Physical observations can often provide clues about gold’s authenticity:

  • Discoloration: Genuine gold doesn’t tarnish. If you notice any green or black marks, it’s a sign of either fake gold or gold plating over other metals. For instance, a gold-plated silver item might tarnish and show the silver beneath.
  • Skin Discoloration: Some people find that wearing fake gold jewelry can discolor their skin green. While this isn’t a definitive test (some genuine gold alloys can cause discoloration in sensitive individuals), it’s a point to consider.
  • Gold Streak Test: Rubbing gold against unglazed ceramic can help determine its authenticity. Real gold will leave a gold streak, while fake gold will leave a black streak.

Advanced Testing Methods

For those looking for more definitive answers, advanced testing methods can be employed:

  • Gold-Testing Kits: Available at many jewelry stores, these kits often contain nitric acid and a touchstone. By rubbing the gold on the touchstone and applying the acid, you can observe the reaction to determine gold content.
  • Nitric Acid Test: Gold doesn’t react with nitric acid. If there’s any reaction, it’s likely the item isn’t pure gold. However, this test can be hazardous and should be done with caution.
  • Touchstone Testing: This involves rubbing the gold on a dark stone and assessing the streak color. Different karats of gold will leave different color streaks.

In conclusion, while gold remains a valuable and sought-after metal, ensuring its authenticity is paramount. Whether you’re a collector, an investor, or someone who inherited a gold piece, these tests can provide valuable insights into your item’s true nature. Always remember, when in doubt, consulting with a professional jeweler or assayer can offer definitive answers.

Conclusion

Norwegian woman wearing gold jewelry
Norwegian woman wearing gold jewelry.

In this guide, we’ve taken a comprehensive look at gold, an element deeply embedded in human history and modern applications. We’ve covered:

  • Physical and chemical properties that make gold unique.
  • Its presence in the universe and theories about its origins on Earth.
  • The biological significance of gold and its potential in medicine.
  • Techniques like assaying to determine its purity.
  • The science behind its various alloys and compounds.

Gold’s significance extends beyond its luster and economic value. Its diverse applications, from technology to medicine, highlight its importance in today’s world. As we wrap up, it’s clear that understanding gold is crucial for various industries and academic pursuits. Whether you’re in the gold trade, research, or just broadening your knowledge, we hope this guide has provided valuable insights into this versatile metal.

FAQs

What are 5 characteristics of gold?

Gold is known for its lustrous yellow color, high malleability, ductility, resistance to tarnish, and its ability to conduct electricity. These unique characteristics have made it valuable for various applications, from jewelry to electronics.

What is the gold element number?

Gold's element number, also known as its atomic number, is 79. This number represents the number of protons found in the nucleus of a gold atom.

What is the gold atomic number?

The atomic number for gold is 79. It identifies gold's position on the periodic table and indicates the number of protons in its nucleus.

What is the density of gold?

Gold has a density of approximately 19.3 grams per cubic centimeter at 20°C. This high density contributes to its weighty feel, which is often used as a quick test for its authenticity.

What are the properties of gold?

Gold possesses several distinct properties that set it apart from other metals. It's highly malleable, meaning it can be shaped into thin sheets; ductile, allowing it to be drawn into thin wires; non-reactive, so it doesn't tarnish easily; and it's an excellent conductor of electricity. Additionally, gold is dense and has a soft yellow glow, making it easily recognizable.

What makes gold so attractive to humans?

Gold's unique physical and chemical properties, combined with its historical significance, have made it a highly sought-after metal. Its lustrous yellow color, resistance to tarnish, and malleability have contributed to its use in jewelry and as a symbol of wealth for millennia.

How do the physical properties of gold differ from other metals?

Gold is known for its malleability, ductility, and resistance to corrosion. It doesn't tarnish easily and is a good conductor of electricity, making it valuable for various applications beyond just jewelry.

Are there any biological roles or implications of gold?

Yes, gold has been found in trace amounts in the human body. While it doesn't play a vital biological role, gold compounds are being explored for potential medicinal applications, including cancer treatment.

Where is gold found in the universe?

Gold is believed to be formed in supernova nucleosynthesis. It's present in the Earth's crust and has been found in meteorites. Recent studies also suggest the presence of gold on Mars and other celestial bodies.

What are the theories about gold's origin on Earth?

There are several theories, including the asteroid theory, which suggests that gold was brought to Earth by meteorites, and the mantle return theory, which proposes that gold was present when the Earth was formed and was brought to the surface through geological processes.

How rare is gold compared to other elements?

Gold is relatively rare. Its rarity, combined with its desirable properties, contributes to its high value. It's estimated that only about 244,000 tons of gold have ever been mined throughout human history.

How is the purity of gold measured?

Gold purity is commonly measured using karats, with 24 karats indicating pure gold. Another measure is fineness, with 999.9 fineness indicating pure gold. The term 'troy ounce' refers to a troy ounce of pure gold content in a gold bar.

What are the common alloys and compounds of gold?

Gold is often alloyed with other metals to enhance its strength and change its color. Common alloys include white gold (with nickel or palladium) and rose gold (with copper). Gold also forms compounds like gold chloride and gold cyanide.

What is gold assaying?

Assaying is a process used to determine the purity and composition of gold. It involves various techniques, including fire assaying and spectrographic analysis, to accurately measure gold content.

How can one check the authenticity of gold?

There are several methods to verify gold's authenticity, including the hallmark test, magnet test, and acid test. Professional jewelers and assayers also use advanced techniques like X-ray fluorescence to determine gold's purity.

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