Oval Opal Brooch in 9ct Yellow Gold

• Carat - A carat (abbreviated "ct") is a unit of measurement used to describe the weight of a diamond or other gemstone, and separately is a unit of measurement used to describe the weight of precious metals such as gold,.
  
  For gemstones, one carat is equal to 0.2 grams or 200 milligrams. The weight of a diamond is one of the Four Cs (along with cut, colour, and clarity) that are used to determine a diamond's value.
  
  It is important to note that a diamond's weight does not necessarily correspond to its size. A diamond's cut, which affects how well it reflects light, can make a diamond of a lower weight appear larger than a diamond of a higher weight. Additionally, the carat is not the only factor to determine the value of a diamond, other factors such as clarity, colour and cut are important too.
  
  In the gold industry, the purity of gold is measured in carats (abbreviated "ct"), with 24 karats being pure gold and lower carat numbers indicating a lower purity level. So, for example, 18 carat gold is 18/24 or 75% pure gold, and 12 carat gold is 12/24 or 50% pure gold.
• Doublet and Triplet - A doublet and a triplet are both composite imitation stones, consisting of two or three joined layers. A triplet is made with the crown and base of genuine material, but with a centre layer, usually of glass, the object being to make the stone appear larger than it really is. A doublet consists of only two layers.
  
  Opal doublets are quite common and consist of a thin layer of opal cemented to an opal matrix or black glass.

This item has been included into following indexes:

• brooches, set with - opal 294