Lexicon

Precious metals

Gold/pure gold (origins)


Discovered approximately 5000 BC, gold was already a sought-after commodity in ancient times. Finds in Germanic graves and excavations in the Nile Valley demonstrate that even 4000 years ago, the working of gold was enjoying a heyday. In the Middle Ages, the gold deposits in European countries had already been exhausted. Following the discovery of America in 1492, it was the gold finds in Mexico, Peru and Brazil which brought the Spanish immeasurable wealth. Gold deposits were discovered in California in 1848, in Australia in 1854, in South Africa in 1880 and in Klondike, in a tributary to the Yukon in North America, in 1896.

Gold/pure gold (properties)


Chemically pure gold is known as fine gold, or pure gold. It is free of all other metals such as silver and copper and can be rolled out to form gold leaf (ca. 1 micrometer). Pure gold is light yellow in colour which does not change when it is exposed to air because pure gold does not bind with the oxygen in the air. Pure gold is the most flexible of all metals. Because it is very soft and pliable, it is mixed with other metals before it is processed (alloyed). Adding silver makes it lighter in colour, adding copper makes it darker. Gold comes in the following colours: yellow gold, red gold, white gold, green gold, rosé and grey gold.

Silver (origins)


Silver is another metal which was known to man even in prehistoric times. It was discovered in around 4000 BC. The Egyptians brought it from Nubia, the Phoenicians, Carthaginian and Romans from Spain. Germany began silver mining in the Harz mountains and in Freiberg in Saxony as far back as the 10th century. Mexico, Bolivia, Peru, Chile and Argentina have been providing enormous quantities of silver since 1521, and the mountainous areas of the United States since 1860.

Silver (properties)


Silver is the metal which has the whitest colour. Because it is so soft, it is not very suitable for processing and so is alloyed with copper. Silver is a good thermal and electrical conductor and so is often used in the fields of electrotechnology, dentistry and photography. Because of its bactericidal effect, silver is often also deployed in the medical arena.

Platinum (origins)


Platinum was still unknown in the Middle Ages. It was not until around 1735 that the Spanish discovered it in the form of small granules in placer deposits in the river Pinto in Columbia. Since not much could be done with this grey metal which, because of its high melting point, was resistant to fire, it was named ‘platina’ or ‘little silver’, a derisive diminutive of the Spanish world ‘plata’ meaning silver.

Platinum (properties)


Platinum is a very heavy metal which is much less fusible than gold and silver, because its melting point is 1774°C. Platinum is harder than gold and silver and exceptionally tough yet at the same time flexible. When polished, platinum takes on a high gloss. Its grey-white colour, which is lightened by adding palladium, ensures it looks particularly beautiful when set against cut diamonds.

Palladium (origins)


Platinum is never entirely pure, it always occurs with five other metals: palladium, iridium, rhodium, osmium, ruthenium. The silver-white metal palladium is always found with platinum, but is also extracted as a by-product of gold, silver and nickel ores.

Palladium (properties)


Goldsmiths use it in place of the more expensive platinum. The benefits are clear. It is somewhat lighter in colour than platinum, it is lighter, cheaper, and becomes highly glossy when polished. A small amount of palladium is usually added to working platinum to lighten the platinum colour. Good white gold also consists of gold and palladium. Platinum also acts as a catalyst for chemical purposes and is used in laboratory equipment and by the automotive industry.

Alloy


Alloys are formed by melting together two or more metals. Goldsmiths work almost exclusively with alloys. None of the three precious metals (gold, silver, platinum) are processed in their pure state. Gold and silver are too soft in their pure state, platinum is not white enough – so they need to be alloyed with other metals to make them more suitable to work with. For example, goldsmiths alloy gold to increase its hardness, to increase the quantity of metal by adding lower cost metals such as silver and copper and to produce gold products at affordable prices. Alloying also enables different gold colours to be maintained.

 

Fineness scale


24 carat = 24 carat pure gold = 1000/- gold
18 carat = 18 carat pure gold + 6 carat Addition = 750/- gold
14 carat = 14 carat pure gold + 10 carat addition = 585/- gold
8 carat = 8 carat pure gold + 16 carat addition = 333/- gold

Cuts

Facet cut


In a facet cut, the stone is cut into a large or small number of geometric faces, usually triangular or square, which are known as facets (facet = face).

Brilliant cut


A brilliant cut is made up a crown and a pavilion which converge at the girdle. On a traditionally cut stone, the crown takes up one third of the entire height. The perfect cut (three-way) has 32 facets on the crown and 24 facets on the pavilion. Most stones of 1/25 carats upwards are cut in this way. Smaller stones from 1/16 – 1/40 carats are cut such that there are 16 facets on both the pavilion and the crown (two-way). Even smaller stones of 1/25 – 1/300 carats have an ‘octagon cut’.

Baguette cut


With this cut, the stone is formed into a very narrow, rectangular shape.

Fantasy cut


Here, the precious stones are cut into a range of different shapes such as a heart, crest or barrel, etc.

Princess cut


Similar to the brilliant cut, the square-shaped princess cut is also of premium quality with lots of facets. It differs from the brilliant cut in that the table (= uppermost flat, horizontal facet) with a princess cut is square whereas with the brilliant cut it is round with lots of increments.

Stone types

Brilliant


Brilliant is the name given to a diamond in the brilliant cut (at least 32 facets on the crown and table and at least 24 facets on the pavilion). The abbreviated designation is permitted only in relation to diamonds, all other brilliant-cut gems must always include the mineral name (e.g. Zircon Brilliant/Zircon in Brilliant Cut).

 

Diamond


The diamond is the cubic, crystallised modification of carbon and is the most valued of precious stones. As a result of its powerful light refraction and colour dispersion properties, it sparkles brightly. The most beautiful stones are as clear as water and transparent, but there are also blue, yellow, brown, green and black stones. Stones develop their beauty only when they are cut. The main cuts are the brilliant and the rose. Value is dependent on the colour, purity, cut and size. Very small stones, so-called octagon and full-cut cuts, are the most expensive because of the high cost of cutting them.

Surfaces

Surface (sandblasted/sand-matt)


A strong matt finish is achieved with a sandblasting machine. These are machines in which the rings are exposed, under continuous revolution, to a stream of fine-particle sand or quartz until a matt surface is achieved. The finer the sand, the finer the matt effect, and vice versa.

Surface (polished)


In this important process, the surface treatment of precious metal objects depends very much on the pre-treatment. Only if the metal surface has been smoothed to perfection through grinding can a flawless finish be achieved.

Surface (matt/silk matt)


While the surface made smooth through grinding gleams when it is polished, matting roughens the surface so that it appears dull and matt. The matt is fine-grained or less fine-grained according to the method applied.

Surface (Hammer stroke)


This surface treatment is a lovingly applied hand-finish. In this process, a chasing hammer with a rounded-down head is used to hammer lots of small indentations into the ring. Rings with such a surface are usually polished. Hammering creates an unusual decorative effect.

Surface (Frosted)


A ‘frosted’ surface finish involves applying structure to the ring using diamond files, a diamond pad or coarse-grained sandpaper in circular movements. The result is visible, unstructured scratching which in interplay with the polished surfaces or sparking gems certainly has its own quite special appeal.

Surface (Transverse frost/longitudinal frost/45°-bevelled frost)


With this type of surface treatment, the piece of jewellery is given its individual structure either with an abrasive non-woven fabric mat, a matting brush or by machine. Transverse frosting results in a lot of short lines (distributed in parallel vertically across the top of the ring), longitudinal frosting results in long lines (once in parallel horizontally around the ring) and 45° bevelled frosting goes from left to right.

Rhodinising


Rhodium is characterised by its high resistance to corrosion and abrasion. With a bright white rhodium coating applied galvanically, for example white gold and platinum jewellery are made lighter and silver jewellery is protected from tarnishing.

Platinising


This galvanic surface treatment can be applied to many metals. Pieces of jewellery are platinised for the following reasons: The platinised coat gives the piece of jewellery a greyish colour so that it looks very similar to a full platinum piece of jewellery. The precious metal below the platinised coat, and which is the main material used to produce the ring, is protected from tarnishing. Furthermore, this process can be used to make pieces of jewellery made from a lower cost precious metal look more precious and thus increase their value.

Settings

Claw setting/prong setting


In this mounting, the stone sits high and is supported by small metal posts (claws). The goldsmith makes the posts from a conical frame. This is then divided with the claws sawn out from the top and the cusp filed from the bottom and a foot ring is then soldered to it. To provide the ring with effective support, the claws are tapped inwards or milled and the remaining claw section pressed over the girdle of the stone and filed. Claw settings are often found on solitaire rings.

Rub-over


The stone is placed in a level plate and held in place by the fact that the edge of the surrounding metal is rubbed a little way above the girdle of the cut stone. The rub-over setting is particularly suited for small stones because only a narrow metal edge is set above the stone and little of the stone is hidden.

Tapping


With tapping, the stone is set in the hole and the metal pressed with a stylus causing shavings which extend over the stone, so fixing it in place.

Tension setting


Round or square stones are set in a ring using tension. They are placed in the stone setting where the metal is compressed. As a result, the stone does not rock and sits fast in the ring.

Blend


(See tapping). A blend setting is the next development along from tapping. With blending, a polish is applied to the edge of the stone. This means that the stones can be set individually or in a row.

Channel setting


(See tension setting) Channel setting is the next development along from tension setting. In a channel setting, several stones are placed in a row, stone after stone.

Other

Crowning


Crowing means the curved inner and outer shape of rings. Inner crowning serves primarily to increase wearer comfort because the ring passes over the finger more easily. This is because of the rounded-down edges.

Carat


Carat can first of all be used as a unit of weight for precious stones. In this case, one carat corresponds to 200 milligrams.
However carat can also be used to indicate the gold content of an alloy using a 24-stage scale (see fineness scale)

Engraving (diamond engraving)


With diamond engraving, a diamond tip is used to etch the text into the ring during which process the diamond tip replaces the material (precious metal). With this type of engraving, it is usually possible to choose between different fonts and symbols but not to create graphics.

Engraving (laser engraving)


Laser engraving uses a highly sensitive laser to burn out the graphic or text to be engraved. This form of engraving opens up completely new opportunities since not only pure text can be applied, individual handwriting or fingerprints etc. are also possible.