Gold
Gold is a chemical element with the symbol Au and the atomic number 79 in the periodical table.
Gold is malleable, non magnetic and does not oxidise in air or water maintaining its colour which makes it ideal in the making of jewellery.
Pure gold is yellow in colour, however gold can also appear to have other colours.
These colours are generally obtained by mixing gold with other elements in various proportions.
For example, alloys which are mixed 14 parts gold to 10 parts alloy create 14 carat gold, 18 parts gold to 6 parts alloy creates 18 carat, etc.
This is often expressed as the result of the ratio, i.e.: 14/24 equals 0.585 (rounded off), and 18/24 is 0.750. the new hallmarking system thus identifies 18 carat as 750, 14 carat as 582 and 9 carat as 375.
There are hundreds of possible alloys and mixtures possible, but in general the addition of silver will color gold green, and the addition of copper will color it red.
A mix of around 50/50 copper and silver gives the range of yellow gold alloys the public is accustomed to seeing in the marketplace.
Gold comes in many colours. the two besr known are;
White gold
Rose gold
However ther are several lesser colours.
Green gold
Green gold alloys are made by leaving the copper out of the alloy mixture, and just using gold and silver. It actually appears as a greenish yellow, rather than as green.
Eighteen carat green gold would therefore contain a mix of gold 75% and silver 25%.
This is often used to fire enamels to as they adhere better to these alloys.
Grey gold
Grey gold alloys are made by leaving the element (nickel, palladium or cobalt) out of the alloy mixture, but adding silver, manganese and copper instead.
Black gold
Black gold is a type of gold used in jewellery.
Black colored gold can be produced by various methods:
Electrodeposition or electroplating using black rhodium or ruthenium. Solutions that contain ruthenium give a slightly harder black coating than those that contain rhodium.
Patination by applying sulfur and oxygen containing compounds.
Plasma assisted chemical vapour deposition process involving amorphous carbon, and controlled oxidation of carat gold containing chromium or cobalt.
More recently a laser technique has been developed that renders the surface of metals deep black. A femtosecond laser pulse deformes the surface of the metal forming nanostructures. The immensely increased surface area can absorb virtually all the light that falls on it and thus rendering it deep black.
Purple and blue gold’s
Purple gold (also called amethyst or violet gold) is an alloy of gold and aluminium. Gold content is around 79% and can therefore be referred to as 18 carat gold. Purple gold is more brittle than other gold alloys, and a sharp blow may cause it to shatter. It is therefore usually machined and faceted to be used as a 'gem' in conventional jewellery rather than by itself. Blue gold is similarly an alloy, this time between gold and indium.
As well as the various colours there are rare regional varieties.
Welsh Gold
Welsh gold is highly prized because of its origin and scarcity, and occurs naturally in two distinct areas of Wales.
One area is in North Wales in a band stretching from Barmouth, past Dolgellau and up towards Snowdonia.
In South Wales it is found in a small area in the valley of the River Cothi at Dolaucothi where it is known to have been mined by the Romans.
Due to its rarity, Welsh gold is usually more expensive to buy on the high street and is often sold in diluted form (with 10% of provenanced Welsh gold mixed with other gold bullion and from another source as little as 0.01% as a token 'touch').
Gold is often sought as a haven aginst bad times by shrewd investors and as such will allways have a realisable value.
Scrap Gold Buyers will buy gold of any colour or carat.
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