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Gold and silver precious metal facts

GOLD CARAT

Pure gold is too soft to use in making objects such as coins and jewellery so is always mixed with another metal. The more gold used the higher the carat number. In the UK the gold content is measured in carats (karats in the US) with the minimum content legally allowed to be called gold being 9 carats where the gold is a minimum of 37.5% of the total weight of the piece. Pure gold is 24 carats - gold bullion is 23.5 carat.

Carat is also used as a measure of weight, especially in measuring gemstones where carat equates to one fifth of a gram. Gemstones are sold by carat, precious metals by the gram, according to the purity of the metal used (eg: 5g of 14ct gold but 5ct of rubies).

The term carat comes from its use by ancient merchants in the Middle East and is based on the weight of the carob bean.

18ct gold is the best quality gold used in jewellery meaning that the metal is 75% pure gold.

14ct gold is 58.33% pure gold.

12ct gold is 50% pure gold.

9ct gold is 37.5% pure gold and is the cheapest gold used in jewellery but perhaps the most durable.

Gold Filled (also known as Rolled Gold)

Gold filled items have a thick layer of gold – which has to be a minimum of 9ct (10kt in the US) –than gold plated items, with the gold comprising at least 5% of the total weight of the piece. The gold is permanently bonded onto another metal – usually brass - using heat and pressure. Gold filled items do not tarnish and are expected to last a lifetime without the gold layer rubbing off.

Gold filled items cannot be cast as carat gold can be as the melting process would destroy the gold layers.

Different manufacturers use different gold carat in their gold filled products – there is no standard carat and gold filled items can be 9ct – 18ct.

Gold Plate or Gold Electroplate

Gold plating is achieved through placing base metal (copper, brass or some other alloy) items in a solution which contains gold (between 9ct and 18ct depending on the quality) then passing an electric current through the solution which deposits the gold in a thin layer on the article. Some layers are thicker than others, depending on the amount of current and length of time used but all will wear off over time.

Gold Vermeil (pron. vehrmay)

Gold vermeil is achieved through the same process as gold plate but using sterling silver as the base metal which makes it ideal for people who have allergies to base metals. Again the quality and thickness of the gold depends on the manufacturer but gold vermeil items tend to be of higher quality than gold plated. The thicker the gold layer and the higher the carat the better. The gold layer should not rub off as easily as gold plated does but there are no minimum standards in the UK – the gold layer can be 9ct gold and fairly thinly applied and still be called vermeil.

DiDi handmade jewellery uses 18ct gold vermeil, with a thicker layer of gold, as a rule.

SILVER

Most silver used in jewellery is a by-product in the refining of other metals, usually lead, zinc, copper and other ores. All silver tarnishes over time but the tarnish can be easily cleaned using a jeweller's silver cloth.

Sterling Silver

Sterling silver contains 92.5% pure silver. The remaining metal is usually copper. Sterling silver finishes can be matt or very shiny, depending on the technique used to finish them. To achieve a high polish items are brushed with a series of fine wire brushes. Sometimes items are not polished in this way but dipped in a melted silver solution to achieve the same high gloss as a fine polish. This finish may wear off, revealing a dull look underneath, but the item will still be sterling silver.

Oxidised silver is where the silver is exposed to a hot liver of sulphur solution which turns the silver black. This is a permanent finish which can be very effective. The same affect can be achieved by placing the silver items in a sealed container with a still hot but broken up hard-boiled egg for half an hour or so.

Argentium Sterling Silver

This is a relatively recent creation where the amount of pure silver (92.5%) is retained but the alloy - usually copper - which comprises the other 7.5% of the metal is replaced with the metalloid germanium a hard silver coloured metal with similar properties to tin. Argentium sterling silver is more expensive than regular sterling silver as there it is not yet produced in sufficient quantities to lower the cost. But it is much better - it doesn't tarnish so readily!

Silver Plate, EPNS

Silver plate is base metal plated with a fine layer of sterling silver using the same electroplating method as is used for gold plated items. The silver layer tends to wear off over time but silver plated components are very cheap and used extensively in fashion jewellery.

Thai or Karen Hill Tribe Silver

The Karen hill tribes of Northern Thailand live in poor conditions on the Burmese/Thai borders where the craftsmen and women make all of the silver by hand through fair trade schemes. The silver used is almost pure, with a much higher silver content than sterling and has a distinctive soft feel and colour to it. It is used extensively in DiDi handmade jewellery.

This is from the Chiang Mai website:

"It was as recently as 1969 that His Majesty King Bhumibol, Thailand's reigning monarch, initiated 'The Royal Project for the Hill Tribes'.

This project was set up to address the problems that were being caused by both their farming methods & also reduce dramatically their reliance on the Opium Crops that flourished all around Northern Thailand at that time.

To address these problems and to also help improve their quality of their lives the King granted the Hill Tribe groups long-term permission to reside within his Kingdom (up until then they had always been just migrants, with no rights at all), they were provided with Thai ID's & land rights. In exchange for this the King insisted they switch farming methods & cease growing the crops of poppies .

It was during the Royal Project that King Bhumibol learned of the Karen Hill Tribes Traditional Jewelry making skills which had been passed down through generations for hundreds of years.

To help "commercialise" these skills he provided them with the silver, tools and a series of contacts that allowed them to become more self sufficient, and within a few years a potentially lost art was revived.

Today, Karen Hill Tribe artisans are taught to carefully handcraft each design from scratch, using only high-content silver (97%-99% pure) & employing traditional methods & tooling.

Each handmade piece is a unique masterpiece that is the result of centuries of Karen Hill Tribe culture and art.

Typically, this beautiful jewelry is engraved with plants, flowers, animals, or geometric designs, symbolizing their direct connection & historical links to both the land and water.

The "distribution" centre for this production is Chiang Mai, the Karen Hill Tribe families still travel into the city once a week to trade their wares as they have done for generations, and from Chiang Mai their distinctive jewelry is then sold and shipped to every corner of the world".

Bali Silver

Some communities within the island of Bali, one of the Indonesian islands, have specialised in silversmithing for generations, using simple tools and pure silver, mined in Indonesia. They mix the silver with copper to make sterling silver, melting it to pour into moulds or to create sheets or wire.

These are used to create the beautiful beads and other components which makes jewellery used with Bali silver so distinctive. Many items are filigree designs, achieved by cutting small holes into the metal, soldering thin wires onto the pieces, and applying granulation. After the beads are formed, they are cleaned with a solution made from tamarind fruit, then oxidized to give the designs their distinctive dark patterns.

Again, DiDi handmade jewellery uses Bali sterling silver extensively.

Tibetan Silver

Tibetan silver is not made in Tibet but is mass produced in China. Although Tibet had a silversmithing tradition many moons ago that has long gone but the name lingers on. Most modern Tibetan silver is cast from a variety of base metals including copper, nickel and perhaps, but unlikely, a small amount of silver. Some Tibetan silver also contains zinc and some older pieces (outlawed in 1999) contain lead.

Many of the designs of beads and jewellery components are a direct copy of Bali silver designs and because of the use of oxidization in Bali sterling silver the darker colour of the base metals used in Tibetan silver helps with the disguise. But the quality is very poor. They are however extremely cheap and Tibetan silver is much used in cheaper fashion jewellery.

Berber Silver

Berber silver is not silver at all, but a mixture of any old metals the Berber tribesfolk of Morocco can get their hands on to melt down and fashion into beads. Many of the designs are based on antique jewellery designs. Unlike Tibetan silver however, Berber pieces are hand made by craftsmen and women and they have a lovely "ethnic" feel to them.

HALLMARKS

According to the Assay Office, anything which is to be described as silver, gold or platinum must be hallmarked if it is to be sold as such, unless it falls beneath the appropriate exemption weight. These exemptions are:

GOLD: All articles with a component to be described as gold in which the total weight of all metal is under 1 gram will not need to be hallmarked.

SILVER: All articles with a component to be described as silver in which the total weight of all metal is under 7.78 grams will not need to be hallmarked.

Most of the gold or silver components used in DiDi handmade jewellery are under these weights, although some are hallmarked, especially the sterling silver components as many manufacturers prefer to have their jewellery or components hallmarked as a guarantee that the metal is what they say it is. The mark most commonly used in sterling silver is "925" which represents the percentage of pure silver – 92.5% - in the piece.

To be hallmarked items have to be sent to the Assay Office where they will test the fineness of the metals and stamp (either hand, bench or laser) the items with the appropriate marks.