Precious Metals
Fine jewelry today uses gold, silver and platinum. These, like all metals, are characterized by the following properties.
- Malleability allows the metal to be worked by hammering or pressure without crumbling.
- Ductility is the ability of a metal to be drawn out into a wire.
- Tensile Strength enables a metal to withstand longitudinal stress without cracking.
- Fusibility means that a metal can be combined with other metals to produce alloys.
- Brittleness indicates a tendency to sudden breaking.
- Elasticity allows a metal to return to its original form.
Precious metals in their pure state are seldom used as they are normally too soft for jewelry. Gold, silver, and platinum are usually combined with other metals, called alloys, to produce a more viable metal.
Of the three precious metals, platinum is the most dense. Thus a ring of a given “bulk” will be heavier in platinum than in gold or silver. This density, as well as other factors, make platinum jewelry much more expensive than gold.
Weights & Measures
Three units of measurement are commonly used to measure fine jewelry metal. All are based on the troy weight system.
Troy Ounce
The troy system originated in Troyes, France, a major business center during the Middle Ages. After Mary, Queen of Scots, married into French royalty, Scotland adopted this weight system.
- A troy pound has 12 troy ounces.
- A troy ounce has 20 pennyweight (dwt) or 31.104 grams.
(Note: Troy ounces and pounds should not be confused with the avoirdupois ounces and pounds used for common measuring in the U.S.)
Pennyweight
Pennyweight is abbreviated dwt. The abbreviation originated in Scotland, coming from a specific coin, the denarius (d), which was the same weight (wt) as a Scotch penny.
Gram
A pennyweight has 1.555 grams.
Buyer’s
Tip
When comparison shopping, be sure to compare weight. A pennyweight is about 1.5 grams. If different jewelers quote weights in different measuring systems, multiply the dwt weight by 1.5 to get the approximate gram weight.