KNOWLEDGE

Gold

Gold is a noble metal, extremely resistant to corrosion and tarnish. It is soft, malleable and ductile.

When used to make jewellery, gold is either used pure (24K or "999.9 gold") or alloyed to various purities (fineness). The more prevalent alloys are 18K (75% pure gold) and 14K (58.5% pure gold).

In making "white gold", no copper is used. White gold is still carat gold, but the presence of silver and nickel or palladium makes it completely silvery.

Relationship between color and composition of Au (gold) - Ag (silver) - Cu (copper) alloys

Alloy

Alloying adds strength to gold. A piece of jewellery set with a diamond or colored stone is invariably made of alloyed gold (ie "carat gold").

Alloying involves adding copper, silver or palladium to gold. Different proportions of these metals impart different characteristics, such as color and hardness, to the alloy. In general, the higher the proportion of copper, the redder the color of the alloy. The higher the proportion of silver, the greener the alloy.

Diamond

Diamond is a crystalline form of carbon, but a rare one. Even rarer are diamonds good enough to make jewellery. The quality of a diamond is measured by its 4C's: Clarity, Color, Cut and Carat weight.

Clarity is how "clean and clear" the diamond is.

Color is how "colorless" the diamond is. Most diamonds show a faint tinge of yellowishness. The less yellow the better. There are pink, green, black and blue diamonds; they can be very expensive.

Color grading scale from totally colorless to light yellow. The differences between one grade and another are very subtle, as can be seen by the number of grades within any one category.

Cut is how well the diamond is cut or "faceted". For a diamond to sparkle, it must be cut into shape with many faces (facets), so that light is refracted to different directions. In the case of a round diamond, it can be shown mathematically that if the facets are cut to the correct angles and alignment, then all the lights entering the diamond will be refracted out of it, giving the diamond the most sparkle it is capable of. The cut determines how glittery the diamond is.

The different facets of a round brilliant cut diamond.		The six most popular shapes of a diamond.
	How a diamond handles light.

Carat weight is simply the weight of the diamond in carats. A carat is 0.2 gram. A diamond's worth goes up almost exponentially with its weight.