properties of gold

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Hi all just found this I found it really interesting so i thought i would post it hope you like it .

Geology of gold

Properties of gold

Gold has had an inestimable effect on human history. It has been crafted, mined, worshipped, plundered, fought over and traded for thousands of years. Today, the search for gold is as eager as ever, despite the vast stocks stored away in underground bunkers. So why has gold held this fascination for humanity?

Its initial attraction is its colour, an eye-catching and characteristic bright yellow with a soft metallic glint. Golds pleasant feel, a combination of its density (19.3 grams per cubic centimetre when pure) and coldness, cannot be duplicated by any other metal. Furthermore, gold can be hammered into very thin sheets or leaves, drawn into wire, cast, carved, polished, heated without tarnishing and easily combined (alloyed) with other metals.

Gold also conducts heat and electricity, reflects light and is untouched by nearly all acids, a property which led alchemists to christen it the noble metal. This combination of properties makes gold very stable in its natural metallic form, and also gives it many uses in electronics, ornaments,jewellery and advanced technology.

The colour of gold is directly related to its purity. Crystallised gold and silver have the same atomic structure and their atoms are nearly identical in size, so that natural alloys of gold and silver are common. Pure, or 24-carat gold, is the brightest yellow, but as the amount of silver increases the colour becomes paler. Pale gold containing more than 20 per cent silver (corresponding to about 20-carat gold or less) has been called electrum. Trace amounts of copper, iron and palladium can also substitute in gold. Man-made alloys of gold with rhodium, iridium or palladium, intended to give gold greater hardness when used in jewellery, have been given names such as white gold. The carat scale is commonly used in jewellery, while in mining, an alternative scale uses fineness of gold, where a figure of 1000 corresponds to pure or 24-carat gold.

Formation of gold

Because gold is very stable over a wide range of conditions, it is very widespread in the earths crust. While its overall concentration is very low (about 5 milligrams per tonne of rock), rich concentrations of gold, forming ore deposits, are known throughout the world. The well-known saying amongst prospectors that "gold is where you find it" suggests its occurrence is unpredictable, but it is now known that certain geological environments favour golds formation.

A popular misconception is that natural gold has cooled from a molten state. In fact, gold is transported though the Earths crust dissolved in warm to hot salty water. These fluids are generated in huge volumes deep in the Earths crust as water-bearing minerals dehydrate during metamorphism. Any gold present in the rocks being heated and squeezed is sweated out and goes into solution as complex ions. In this form, dissolved gold, along with other elements such as silicon, iron and sulphur, migrates wherever fractures in the rocks allow the fluids to pass. This direction is generally upwards, to cooler regions at lower pressures nearer the Earths surface. Under these conditions, the gold eventually becomes insoluble and begins to crystallise, most often enveloped by masses of white silicon dioxide, known as quartz. This association of gold and quartz forms one of the most common types of "primary gold deposits".

Veins and reefs of gold-bearing quartz can occur in many types of rock, for example around granites, in volcanic rocks or in regions of black slate, but in most cases these host rocks are not the immediate source of the gold.

Gold deposits have formed at many different times during Earths history. For example, those in Western Australia are believed to have formed about 2400 million years ago, during a period of intense metamorphism and intrusion of igneous rocks. The gold-bearing quartz reefs in Victoria are significantly younger, about 400 million years, but also owe their origin to a period of intense metamorphism in the region.

As chemical weathering and erosion gradually break down the host rocks and lower the land surface, the quartz and gold veins are eventually exposed to the atmosphere. The veins provide far more resistance to chemical attack than the surrounding rocks, so that mechanical weathering is required to fragment the quartz, thereby releasing the gold. Because they are relatively heavy, particles of gold are more difficult to move and so become naturally concentrated in the soil or in adjacent gullies or streambeds. These concentrations are known as alluvial or placer deposits and have yielded incredible riches on some goldfields, such as those in California and central Victoria.

Alluvial deposits take many forms, including sands and gravels in the beds of modern-day streams, in old river valleys buried under lava flows or perched on hilltops due to uplift of the land surface. The terms shallow and deep leads are used in Victoria for gold-bearing gravels covered by younger sedimentary layers or lava flows. These were especially important in the Ballarat district. Because of its resistance to chemical attack, gold can be recycled from one type of alluvial deposit to another.

Types of gold

For such an apparently simple element, the mineralogy of gold is quite complex. To begin with, gold can occur in a wide variety of forms. In massive quartz reefs, gold occurs as disseminated, irregular grains, scales, plates and veinlets with microscopic dimensions, and as larger compact, reticulated, spongy or hackly masses or slugs.

Gold occasionally takes forms that lend themselves to descriptive terms such as wire gold, nail gold, mustard gold and paint gold. While all gold has a crystalline structure, distinct crystals showing well-formed faces are relatively rare. They require special conditions to form, in particular space in which to grow. Hence crystals of gold are found in cavities in quartz reefs or in softer minerals such as iron oxides where they have been able to push aside the enclosing material as they grew. Gold crystallises in the cubic system, and perhaps the most common variety is the eight-sided octahedron.

Possibly the best surviving Australian specimen is a group of sharp, branching, octahedral crystals from Matlock, in the Woods Point goldfield of Victoria. A superb 715 gram (23 troy ounce) mass of crystals known as the Latrobe Nugget was found in the Heathcote district in Victoria and obtained by the British Museum in 1858.

Other important metal-bearing minerals can also be found in the quartz reefs with the gold. The presence or absence of these minerals can be used to help classify the type of gold field. The most common and widespread are pyrite and arsenopyrite, two minerals containing iron and sulphur. This assemblage is distinctive in many of the Victorian goldfields. Sulphides of lead, zinc, silver, bismuth and antimony also occur and may be locally abundant in some gold fields. Massive deposits of these metal sulphides may contain only small proportions of gold, but their overall size makes them significant producers. In the famous Golden Mile at Kalgoorlie, Western Australia, unusual minerals containing tellurium combined with gold have been extremely important.

The relative softness of gold means it can be scratched by harder grains during erosion and transport. However, golds malleability often leads to particles being bent or twisted, rather than reduced in size. Gold grains that havent travelled far from the quartz reefs often preserve many of their original features, such as their basic shape or the imprints of quartz crystals. Generally speaking, finer gold particles known as gold dust have been carried further from their source reefs, possibly by fast-flowing streams. A common observation by early Victorian diggers working alluvial deposits along streambeds was for the gold particles to become smaller and more worn further downstream. This was especially evident in the Woolshed Valley in the Beechworth district in northeastern Victoria, where Reedy Creek flowed vigorously through a steep-sided gorge cut in granite.

Australias gold bearing potential

Australia produces about 300 tonnes of gold annually, currently ranking it about fourth in the world. Exploration for gold continues to be a major activity for Australian mining companies, with target areas extending to the South Pacific and Southeast Asian regions. Whether a discovery is ever mined depends greatly on the size and nature of the deposit and its geographic position, the concentration of gold in the rocks (known as the grade) and, perhaps most importantly, on the international price of gold. Despite some rich deposits being brought into production, none have changed the course of a nation like the fabulous finds of the 1850s.
 
Millions,billions of years, that implies that we evolved from a pool of slime,until someone can provide me evidence that a single cell( which by the way, contains about a billion components) can self assemble all on it`s own, i will not believe in this claptrap. Proof anyone?
The rest is an interesting read!!!
 
Thanks Pete for a very interesting article. And Ironrock, nothing is cast in "gold". The above article gives a believable interpretation of how it all happened. Is it absolutely right? I don't know, you don't know, nobody knows. Guess until someone can come up with an irreputable (hope the spelling is correct) explanation as to causation, then we can only take on board explanations that at least appear to be acceptable.
 
Gold I think you will find as are all the other minerals,as well as the gasses,ie. oxygen,hydrogen,helium ect. are found throughout the universe in various forms & quantities.
 
Regardless of all things either way the coin flipped or flopped, we and the gold happen to be here together, luckily for us all. :| 8) :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: 8) :lol: :lol: :lol: :lol: :lol: :lol: :lol:
A&S rule.
 
Your most welcome i found it a good read .dont know what ironeock is on about and personly dont give a s### .take it like it was intended as an insight as to how gold forms not on how we got here shit if i had the answer to that one i would know where all the gold was hiding lol.glad the rest of you enjoyed the read . :D
 
BigWave said:
Thanks PP, as it was a very interesting read. Learned a bit and consolidated a bit.
ironrock - this does not involve religion, so leave your slime pits be -we are talking gold pits here!
Agreed - it is not discussing anything to do with life or evolution.....just the age of planets (based largely on isotope decay) and their rocks and minerals. Introducing religion as a segue is not very appropriate in this venue - science and religion are different belief systems, based on different assumptions and evidence.
 
https://www.bing.com/videos/search?...3EF54297C77F34285A7A3EF54297C77F&&FORM=VDRVRV

The scientific argument, based on matching evolving fossil forms with the date of the rocks that enclose them.

Many people including a number of scientists find no conflict between science and religion (only between science and fundamentalist biblical literalism). People have every right to believe whatever they want to, but there is a case for understanding what the other person is saying.

None of this has much relevance to the average prospector, but it is relevant to the discovery of large new ore deposits (eg the greenstone belts of WA, Canada, Brazil, South Africa are all of one age - so if you want to find a new Kalgoorlie there is a case for looking in rocks that scientists date of that age). If you want to find Ernest Henry's (as in Australia and Brazil), the rocks are of a different age. Ditto for another age (Bendigo or Nova Scotia.), or another age (Cripple Creek or Lihir).
 
Agreed - it is not discussing anything to do with life or evolution.....just the age of planets (based largely on isotope decay) and their rocks and minerals. Introducing religion as a segue is not very appropriate in this venue - science and religion are different belief systems, based on different assumptions and evidence.
I don't know where ironrocks head space was coming from but I certainly didn't get a hint of religion from his comments, he was just having a bit of a rant.
 
I don't know where ironrocks head space was coming from but I certainly didn't get a hint of religion from his comments, he was just having a bit of a rant.
What alternatives are there to the scientific explanation other than a religious (creation) explanation - is there some third alternative that I have not heard of? He says "until someone can provide me evidence that a single cell.....can self assemble all on it`s own, i will not believe in this claptrap" (i.e. rejection of evolutionary processes). He also objects to "Millions, billions of years", So I think it is clear that he (very strongly) chooses the alternative to the scientific explanation, and favours that some intelligent being created it (commonly called religion) - as Bigwave, Pirate Pete and I interpreted his meaning to be, .

I don't think it matters greatly, but "I believe" leaves less room for discussion than "I believe because a and b and c etc" The first is just personal opinion (to which everyone is entitled), the latter is based on measurable evidence and processes agreed by millions of scientists, and gives room for discussion. Two different belief systems, and many people believe both unless they are specifically creationists. Does it matter otherwise?

Coming back to the scientific belief system, another point is that elements form from burning out of stars but in the main only up to atomic number 40 (iron). Heavier elements like gold appear to require the energy generated during explosion of supernova or collision of neutron stars. And the gold you are holding may therefore be much older than the earth's 4.6 billion years.
 

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