A Jeweler is a person who designs, makes, repairs, or sells jewelry. Jewelry (jewellery in the UK) is small decorative items worn for personal adornment, such as brooches, rings, necklaces, earrings, and bracelets. Jewelry may be attached to the body or the clothes, and the term is restricted to durable ornaments, excluding flowers for example. 

In creating jewelry, gemstones, coins, and other precious items are often used.  Jewelry is typically set into precious metals and alloys (e.g., bronze, gold, white gold, platinum, palladium, titanium, or silver).  Most American and European gold jewelry is made of an alloy of gold, the purity of which is stated in karats, indicated by a number followed by the letter K.

The Jeweler library contains functions and data related to estimating the carat weight of diamonds and other gems and current value of amounts of precious metals in bullion and alloys in bars, coins and jewelry.

Shown above are precision jewelers scales.  When a diamond or other gemstone is not in a setting, precision scales are used to determine the carat weight.  However, when a gem is in a setting, it is often impossible to remove the gem from the setting without doing damage.  In these cases, formula have been developed to estimate the carat weight of a diamond or other gem based on its shape, dimensions and the specific gravity of the type of gem.  Many of these formulas can be found below.