Mineral Collecting Articles

Untitled Document


by Eric Greene

156 ounce gold nugget found in the Mojave Desert in California
in the 1970s


"Mmmmmm, smell that? You mean you can't smell that?
You sure? What is that???
Whaddya mean what is that??
That's the smell of GOLD, that's what!"

- Jim Rocha


The allure of gold has gripped people for over five centuries. Through the years, gold has held a fascination that comes from both its beauty and from its enduring economic value. Gold was chosen early on for use as currency because it was available, but relatively rare, and because it is easily worked into coins and artistic creations. Today, fine specimens of gold are highly desirable because they are both highly aesthetic and also make good investments.

Good gold specimens are worth far more than their value based on weight alone. For example, a gold nugget weighing one ounce is said to be rarer than a five-carat diamond, and may be worth as much as $100 more by weight than gold bullion. Gold crystals, which are even scarcer, aren't even priced by weight, but can command prices up to 10 times higher than their weight value.

Gold is a shiny, soft, malleable, dense metal with a bright yellow color and metallic luster. It is virtually indestructible, and has been used and reused for thousands of years. Today, all the gold known to exist is nearly equal to all the gold ever mined. Gold is the chemical element Au, from aurum, the Latin for gold:

= Its atomic number is 79
= Its atomic weight is 196.97
= It has a melting point of 1948°F (1064°C)
= It has a density of 19.3 grams per cubic centimeter (extremely heavy).

It has been a highly valued and sought-after precious metal for making coins, for creating jewelry, and for other arts since before recorded history began. In all human history, only about 175,000 tons of gold have been mined, That's enough to make a cube 67 feet on a side. 50% of newly mined gold is used in jewelry, 40% in coins and investments, and 10% in industry.

One of the most unusual characteristics of gold is its malleability: An ounce of gold can be beaten into a thin sheet that is about twelve feet wide on each side. This is called gold foil, which is so thin that it is translucent (which is why it has been used in making astronaut's sun visors).


In fact, gold is so soft that it is usually alloyed (mixed) with copper, silver, platinum, bronze, and other metals to make it harder:

= 24K gold is 100% gold.
= 18K gold is 75% (18 parts gold and 6 parts of other metals).
= 14K gold is 58% gold (14 parts gold and 10 parts of other metals).
= 12K gold is 50% gold (12 12 parts gold and 12 parts of other metals)

Gold is a good conductor of heat and electricity, so it is used to make electrical connectors and printed circuit boards. It won't tarnish when it is exposed to the air, making it highly suitable for coins and jewelry.

Other physical characteristics include:

= Color: golden yellow
= Luster: metallic
= Transparency: opaque
= Crystal System: isometric. Habits include massive nuggets, grains in other rocks, wires, octahedral crystals, wires, and dendritic and arborescent crystal clusters.
= Cleavage: none
= Fracture: jagged.
= Streak: golden yellow
= Hardness: 2.5 - 3 (very soft)
= Melting Point: 1063º C
= Specific Gravity: 19.3+ (extremely heavy even for a metallic mineral)
= Associated Minerals: quartz, nagyagite, calaverite, sylvanite, krennerite, pyrite and other sulfides.
= Other Characteristics: ductile, malleable and sectile, meaning it can be pounded into other shapes, stretched into a wire and cut into slices.

Gold is not attacked by acids, except aqua regia (nitro-hydrochloric acid), meaning "dissolves gold." In mining, gold is dissolved in an alkaline solution of cyanide, and also dissolves in mercury in a retort.


Native gold occurs as nuggets, in veins and in alluvial deposits, and as grains in rocks. There are few gold ores that are combinations with other minerals, because it does not combine easily with other elements. Generally, gold is mined from either hard rock deposits (lodes) or placer deposits (river washed).


Gold prospectors who find a lode deposit of gold try to determine the average gold content (by fire assay) per ton of mineralized rock, and also the size of the deposit. to determine its value. Placer deposits contain gold that was eroded from lode deposits. In stream deposits, gold is concentrated on or near bedrock, and amass in sand and gravel bars where the stream current slows down and drops the gold.


Since 1990, many new gold mines opened to exploit low-grade deposits. The area around Carlin, NV, where there are now 7 open pit mines operating, is now a major mining district. Another source for gold is as a byproduct of mining for other metals such as zinc, lead and copper. These account for 15% of the gold produced annually in the United States.


Gold is also present in seawater, but there is no known way to extract it economically. Nevertheless, swindlers have run numerous scams claiming that they have discovered the secret. Needless to say, the foolish investors lost every cent they spent.


Gold is used in many ways - to make coins, jewelry, dental filling, circuit boards, and it can even be eaten!


Monetary exchange
For centuries, gold was the common basis for monetary exchange values. In the late 20th century, the gold standard was abandoned, and was replaced by fiat currency - a term that describes money that is backed by government decree only. In 1999 Switzerland abandoned the gold standard; it was the last country in the world that still linked its currency to gold.


Many people buy gold as a hedge against inflation or as an investment they hope will increase in value. The most popular form for buying gold is gold coins. Popular choices include the American Eagle, South African kruggerand, and the British sovereign, all minted in 22k. The Canadian Maple Leaf gold coin is 99.99% pure, so it has become a popular choice as well. Economists argue that gold is neither a safe investment nor a good inflation hedge, though the recent record high spot gold prices does not back this up.

Price chart of raw melted gold (spot price)

Because of its beauty, the fact that it never tarnishes, and because of its popularity and symbolism, gold has been a popular choice for jewelry for thousands of years. Gold can be worked into almost any shape - from rings to chains to wires to findings. Gold-filled jewelry is made from a layer of gold bonded to an inexpensive mineral like brass. Also, goldsmiths use gold solder to assemble components of gold jewelry.

In medieval times, gold was thought to be beneficial for the health, and that belief is continued today by people interested in using minerals for healing. Today, gold has many uses in modern medicine. It has been injected to treat rheumatoid arthtritis, and has also helped patients with tuberculosis. In dentistry, gold is frequently used for fillings, crowns and bridges. Also, a gold isotope is used to treat some kinds of cancer and other diseases.

Food and drink
Gold is harmless to the body, since it is inert and has no taste (or nutritional value. Gold in the form of flakes, dust or gold leaf is used today as both a decoration and as an ingredient in expensive gourmet foods - especially desserts and liqueurs. Today as in ancient times, this practice creates a grand impression, demonstrating the immense wealth of kings and millionaires.


Gold has many uses in industry. For example it is used to produce an intense cranberry red color in glassmaking, in color photography to create special colors and to increase print stability. It is also employed as a coating on astronauts visors to protect them from infrared, visible light, and radio waves, as a reflective layer on CDs, for de-icing airplane window, and in high-end automobiles to dissipate heat. Gold is especially useful in electronics, where it is utilized in high-energy electrical wiring. Because of its high conductivity and resistance to corrosion, it is also used on circuit boards, switch contacts, and semiconductor devices.

Arts & Crafts
Gold is used in gold thread for embroidery, and as gold leaf for gilding.


Because of its popularity with royalty, gold has come to symbolize great value, wealth and prestige. It also denotes power, warmth, happiness, purity, and love. At the Olympics and for the Nobel Prize, winners are given a gold medal to honor their achievements. Academy Award winners are given a gold statue, and winners of other competitions may be awarded gold cups (usually just gold plated). In ethics, there is a "golden mean", and in mathematics and the arts a "golden ratio". Credit card companies give their best customers "gold cards"; there's the "golden rule" (treat others as you would want them to treat you); a golden wedding anniversary celebrates 50 years of marriage; and "silence is golden". People refer to our age after 65 as the "golden years", and the pinnacle of a civilization is it's "golden age". Wedding rings are traditionally made of gold; royalty wear golden crowns; people are said to have "a heart of gold"; and when things go very well, people say, "then you're golden!"


Throughout history, gold has played an important role in many civilizations.

= Gold artifacts were found in the Balkans that date back to 4500 BC,
= Golden hats and discs from the Bronze Age (around 2000 years BC) have been found in the Balkans,
= The earliest known treasure map is the Turin Papyrus, from 1160 BC. It shows both the geologic formations and location of a gold mine in southern Egypt.
= Ancient Egyptians ate gold as a way to purify their minds, bodies and spirits.
= In Vedic India, gold was associated with the sun, purity, immortality, truth and splendor.
= For centuries, the Chinese have traditionally owned gold for good luck.
= The Greek story of Jason returning with the golden fleece may have referred to the ancient use of sheep fleeces to trap gold dust in placer deposits.
= Gold is mentioned frequently in the Old Testament, and was one of the gifts the magi brought to Bethlehem
= The earliest gold coins were made in Lydia around 600 BC, and square gold coins in China date to about 500 BC.
= The Romans invented hydraulic gold mining around 25 BC.
= In 1324 AD, the emperor of Mali rode through Cairo with a great retinue of followers, and gave away so much gold that the price of gold was depressed for the next 12 years.
= In Middle Ages Europe, many countries established gold as their base currency.
= During the same period, the alchemists tried to turn lead into gold, using processes that became the basis for modern chemistry.
= Spanish conquistadores seeking Aztec and Inca gold explored the Americas in the mid-1600's.
= In 1804, a gold rush in North Carolina led the way for later rushes in California, Colorado, and the Klondike.



Nuggets are naturally occurring pieces of native gold that were broken off of the original gold vein, and then carried by water and erosion to a new location. Nuggets are always very popular with collectors. In his day, Hollywood legend John Wayne had a belt buckle made using 13 gold nuggets, with a total weight of over 13 troy ounces.

John Wayne's gold nugget belt buckle

But nuggets are rare: Less than 1% of the world's gold is still in nugget form, which is why nuggets sell for a much higher price than gold bullion. Gold coins also command a premium price, depending on condition, purity, and rarity. The value of nuggets is determined by other factors: weight/size, color, brilliancy, rarity, origin, and so on. Purity is not a factor, because it's not possible to assay every nugget, and because doing so would damage the specimen. Most nuggets are between 20k and 22k - which is 83-92% pure.

"Welcome Stranger", the worlds largest gold nugget weighed 276 pounds (2332 ounces); it was found in 1869 in Moliagul, Victoria, Australia. At today's bullion price, it would be worth over $3.7 million!

The rarest and most valuable form of gold is gold crystals. The American Museum of Natural History website says that gold crystals can be worth 7 times as much as gold bullion! Crystal habits include octahedra, cubes, dodecahedra, wires, herring bone, and dendritic and arborescent crystal clusters. Most crystallized gold sold today is dissolved out of quartz using hydrofluoric acid. Nuggets may still contain crystals which were not beaten by erosion.

1.2" 21.2 gram gold nugget with octahedral crystals - Sonora, Mexico


Gold Wires
Wire gold specimens are quite rare. In Colorado, the Breckenridge District was famous for its fine wire crystal gold specimens. In the early mining days, many fine specimens were melted down for their bullion.

Wire gold, Wire Patch Mine, Breckenridge, Colorado, Nevada Outback Gems photo


Ribbon and Foil Gold
When people think of gold foil, most people think of gold that has been rolled or hammered into thin sheets. Occasionally, gold naturally forms in leaf-like sheets or ribbons that have not been beaten flat. Due to their rarity, these make interesting and unusual specimens of native gold.

1.1" 0.8 gram native ribbon gold - Round Mountain Mine NV


Quartz Gold
Gold-bearing quartz veins are one of the rarest ways that gold occurs naturally. Today it is primarily found by hard rock miners, usually mining for specimens. The more famous California locales for this type of gold are the Eagle's Nest Mine in Placer Co., Sixteen-to-One Mine in Sierra Co., the Colorado Quartz Mine, Mariposa Co., and Tuolumne Sunshine Mine, Tuolumne Co. These specimens are found by placing a piece of gold-bearing quartz in hydrofluoric acid, which dissolves the quartz but leaves the gold untouched.

Display of California crystallized gold in quartz at the 2009 Tucson Gem & Mineral Show.
The specimen in the middle, called "The Dragon", is over 5" tall

Mineral dealer, collector, and curator Ron Bentley recounted my favorite story about a gold in quartz specimen. In 1981 he was hired as a consultant to help oil billionaire Perkins Sams build a collection of world-class specimens. Returning from a buying trip to Europe, he showed Sams a specimen of gold in quartz from California which he had purchased. Sams asked him why he had bought it (for $10,000), and said he wasn't interested in junky specimens like that. Bentley offered to buy it back, and explained that it had not yet been treated in hydrofluoric acid. Sams declined the offer, and when the specimen emerged from the acid, it became the centerpiece of his gold collection!


Dendritic Gold
Dendritic means "branching like a tree," so dendritic gold has a diverging structure. It is also called arborescent gold.

1.2" Dendritic gold, Round Mountain Mine, Nye Co., Nevada

About 2471 tons of gold are mined every year, at an average cost of $317 per ounce. The most economical way to mine gold is large deposits which can be mined using the open-pit method. Profitable ore grades in an open pit mine can be as low as 1- to 5-parts per million. South African mines, some as deep as 3,777 meters, have yielded about half of all the gold ever produced. In 2007 China surpassed South Africa as the world's number one gold producer. Other major gold producers include the United Sates, Australia, Russia, and Peru.


About half the gold consumed in the world is used in jewelry; 40% goes for investments, and almost 10% is used in industry. India is the largest gold consuming country in the world, buying 25% of the annual production each year. Most gold used in jewelry, electronics, etc. is recovered and reused, leaving an estimated 85% of all gold ever mined still in use.


Notable occurrences for nuggets and specimen gold include California, Alaska, and Nevada in the United States; Siberia in Russia; Victoria, New South Wales, and Wetern Australia in Australia; the Yukon, Ontario, Quebec and British Columbia in Canada; and in many other locales throughout the world.