General Information

Objective

To help to develop an understanding of the metals used in jewellery and their properties in order that we might sell them more effectively.

Relevant
Terminology:

MALLEABILITY: The ability of a metal to be hammered and shaped without breaking or being damaged.

DUCTILITY: The ability of a metal to be drawn into wire.

REFLECTION: The ability of a metal to return light rays.

Metals used in Jewellery:

Gold, Copper, Zinc, Aluminium, Silver, Platinum, Rhodium, Palladium & Iron.

Gold:

* Lustrous yellow
* Most malleable of all metals
* Most ductile of all metals - 1oz. can be drawn into a wire 50 miles long.
* Does not form any oxides
* Unaffected by common acids and alkali exc. - mercury

Silver:

* Lustrous white metal
* Most reflective of all metals - up to 98% of all rays returned
* Highly malleable
* Highly ductile
* Will not oxidise at room temperature
* Forms silver sulphate in industrial atmospheres and turns black

Palladium:

* Greyish metallic lustre
* Highly malleable and ductile
* Does not oxidise
* Has by and large replaced platinum due to its similar physical properties.
   It is less expensive and has a lower melting point.

Platinum:

* Greyish white metallic lustre
* Highly malleable and ductile
* Extraordinarily resistant to corrosion and chemical attack

Rhodium:

* Widely used in the plating of white gold and silver
* Highly reflective with brilliant white lustre
* Becomes eight times harder when electrodeposited on metal
* Impervious to all acids and forms of corrosion

N.B. Gold and silver are too soft to use in their pure form and are therefore alloyed with other metals to give them strength.

Carat refers to the units of gold to alloy - 24ct refers to pure gold, 18ct to 18 parts gold, 6 parts alloy etc.

European system uses 1000 as pure gold, 750 as 18ct etc. Alloys not only strengthen gold, but also alter its colour. See chart attached.

Rolled or Gold
Filled:

Usually stamped 1/10 or 1/20th 9ct gold meaning the proportion of 9ct gold to total metal content by weight. Rolled gold is produced by sandwiching a layer of base metal, usually brass, between two layers of gold. The gold is fused to the base metal by heat and pressure.

Hard Gold Plate:

Has replaced rolled gold largely because it allows the manufacture of more intricate pieces in gold.