Metal, the Jeweller’s Raw Material

The word metal is akin to the Greek word Metallan, “to search after” from the Greek Metallon, in Latin, Metallum, both meaning “a mine or metal”. Jewellery has been and still is made of many other materials, but jewellery making remains essentially an art of applying technology and metals. Of more than 70 metals exist, about 40 have commercial influence and approximately half that number are used in jewellery itself, or to assist in jewellery making or lapidary. (Gemstone cutting)

 

Metal Characteristics in General

Metal is a natural elemental chemical or mineral substances each possessing a distinctive, crystalline atomic structure. As compared to non-metallic elements, metals are heavy, and they are (except for mercury) opaque and solid at normal temperatures. When they are mined or extracted from natural deposits in the earth, they sometimes are found in a native or pure state. More commonly, they occur as ores, which are crude, natural compound minerals containing several components, including one or more metals; the rest is non-metallic waste matter. These metals are then extracted from these compounds.

 

Metal Groups

Non-Ferrous Metals

This group contains the noble or precious metals and base metals which contain iron. Noble metals include gold, silver and so called platinum, six-metal group (platinum, palladium, rhodium, iridium, osmium, ruthenium) They are “noble” because, rarity aside, they are highly stable chemically, and resist oxidation and corrosion from acids, qualities especially attractive when they are made into jewellery and other objects.

 

Base Metal

Base metals are so called because they are abundant and not precious. Included in this group are aluminium, copper, lead, mercury, nickel, tin, zinc and many others not ordinarily used by jewellers.

The light metal group includes metals with low densities: aluminium, magnesium, titanium and alloys in which these metals are basic. Another division is the refractory metal group, metals with high melting points (above that of iron): Titanium, niobium, tantalum, platinum, palladium, rhodium and their alloys.

 

Ferrous Metals

Ferrous metals are iron and ferroalloys (alloys which contain iron) such as steel, essentially and alloy of iron and carbon plus small amounts of other metals. Two or more elemental metals can be combined to make a compound or alloy. This is done to change visual properties such as colour, or working properties such as hardness, denseness, corrosion resistance, or to lower the melting point of the base metal in the alloy. Heat and fusion are used to mix and unite the components. Base metals are alloyed with each and also precious and ferrous metals. Precious metal alloys are still considered “precious” as long as certain standard recognised proportions are maintained in which the precious metal normally dominates. For example, gold items of jewellery, before hallmarking, are tested to make sure that the right content of the precious metal exists within the alloy by law.

 

 

Technical Information

What is a hallmark?

A hallmark means that the article has been independently tested by an assay office and guarantees that it conforms to a specified legal standard of purity. This is called the fineness of the metal and the precious metal content is expressed as a millesimal number. For example, the number 999 means the metal is 99.9% pure.

Click here to see the Hallmarking chart.



Gold

Wedds

Types of Gold




22ct Gold

•    Only available in yellow.
•    Not used so much in this country today.
•    Its bright colour is not very popular with the consumer.
•    Used primarily in India and most of the Arab countries.
•    Hallmarked-916.


18ct Gold

•    Available in yellow, white and red.
•    This is the most desired carat gold.
•    18ct alloys are better in colour and contain more gold.
•    Hallmarked -750.

The 18ct white gold that we use in our manufacturing is a high percentage palladium alloy that does not required Rhodium plating.

9ct Gold

•    Used in Britain but not really abroad.
•    Available in yellow, white and red.
•    Generally used if the customer is on a budget.
•    Hallmarked-375

N.B. Precious metal purities are worked out by parts per thousand
e.g. 18ct. 750 parts of a thousand are gold. The other 250 parts are the suitable alloys mixed with the gold for specific manufacturing reasons i.e. for colour and strength.

Some examples:

•    Copper when added to gold gives it a red colour and hardens it.
•    Palladium mixed with gold makes it white and hardens it.
•    Silver when added to gold hardens it, in conjunction with added copper. It also whitens its colour.

What is plating?

Plating is a surface covering in which a metal is deposited on a conductive surface. In this case gold is deposited on the surface of the silver.


Rhodium Plating

Rhodium is a chemical element that is a rare, silvery-white, hard, and chemically inert transition metal and a member of the platinum group.
It has the chemical symbol Rh and atomic number 45.
Rhodium is a so-called noble metal, resistant to corrosion, found in platinum or nickel ores.
Because rhodium metal is inert against corrosion and most aggressive chemicals, and because of its rarity, rhodium is usually alloyed with platinum or palladium and applied in high-temperature and corrosion-resistive coatings
 White gold is often plated with a thin rhodium layer to improve its appearance while sterling silver is often rhodium plated for tarnish resistance.
Rhodium is a very precious metal that can cost ten times as much as gold or more!
Rhodium finds use in jewellery and for decorations. It is electroplated on white gold and platinum to give it a reflective white surface. This is known as rhodium flashing in the jewellery business.
Rhodium is hypoallergenic, so it won't react with your skin.
Solid (pure) rhodium jewellery is very rare, because the metal has both high melting point and poor malleability (making such jewellery very hard to fabricate) rather than due to its high price.
How long will it last?
This can depend on whether the item is a ring (rings suffer a great deal of wear), or a pin or broach which receives almost no contact. And it depends on whether you wear the ring constantly. Normally, with a ring Rhodium plating will eventually wear off and should be reapplied every couple years.

Gold Plating

Some pieces of jewellery, for various reasons, are plated with 9ct or 18ct yellow gold and red gold.


Platinum
Platinum
•    Hard white metal.
•    The rarest and heaviest of all the precious metals.
•    Resistant to scratching and oxidation.
•    Hallmarked-950.


Palladium
Palladium
•    A bright white metal.
•    Primary whitener of gold, especially in 18ct alloys. It also raises the melting point.
•    Comparable in colour to platinum and is from the platinum group of metals.
•    It is not as hard and dense as platinum but can still sustain heavy wear.
•    Its lower price makes it a popular alternative to platinum.
•    Hallmaked-950.

N.B. It is also available in a lower purity but this is the one we use.

Silver
Silver
•    A stunning metal with a brilliant white lustre in its purest form.
•    Occurs organically in ores.
•    Electrolytic copper refining can also recover the metal.
•    Harder than gold but still malleable.
•    Commercial fine silver is at least 99.9% pure.
•    Sterling silver is the most common form of silver seen at present.

Sterling Silver

•    Used in the production of jewellery.
•    An alloy combining 92.5% silver and 7.5% copper.
•    Hallmarked-925

Cleaning Tips

A reduction in oxidisation can be achieved with a polishing cloth. Although it does not prevent it, it does help in reducing the effects caused by the jewellery being oxidised. It is also recommended that calling into your local jeweller to have the item polished is also beneficial.

Titanium

•    Discovered in 1792 in Cornwall by Rev. William Gregor.
•    Named after the Greek god titan -‘son of the earth’
•    Pure titanium metal is man-made from the titanium mineral.
•    Unaffected by chlorine and sea water.
•    As strong as steel but far lighter.
•    Highly durable-very resistant to corrosion.
•    Hypoallergenic qualities-friendly to your skin.

Coloured Titanium

Though naturally grey in colour, titanium’s vibrant colours are achieved by passing an electric current through the metal. This creates a clear oxide layer on the surface which diffracts and reflects white light, absorbing some colours of the spectrum and allowing others to shine through. This is the same effect seen on the wings of a dragon fly or oil on water.

Did you know?


Titanium is found in meteorites, the Sun, stars, moons, the Earth’s crust and even human bodies.

Stainless Steel

•    Does not corrode or rust with water as ordinary steel does.
•    Used where both the properties of steel and resistance to corrosion are required.
•    It differs from carbon steel due to the amount of chromium present.
•    Unprotected carbon steel rusts readily when exposed to air and moisture.

Tungsten Carbide


•    An inorganic chemical compound containing equal parts of tungsten and carbide atoms.
•    A fine grey powder in its most basic form
•    It can be pressed and formed into shapes.
•    Used in industrial machinery, tools and abrasives as well as jewellery.
•    Approximately three times harder than steel
•    Denser than steel or titanium.