Diamond and Emerald Butterfly Brooch by Mappin Brothers

• 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.
• Circa - A Latin term meaning 'about', often used in the antique trade to give an approximate date for the piece, usually considered to be five years on either side of the circa year. Thus, circa 1900 means the piece was made about 1900, probably between 1895 and 1905. The expression is sometimes abbreviated to c.1900.
• Emeralds - Emeralds have been used in jewellery making for thousands of years, and are prized for their deep green colour, which is caused by the presence of chromium and vanadium in the mineral beryl. Because of their rare colour, emeralds are often more valuable than diamonds of a similar size and quality. In jewellery making, emeralds are typically cut into round or oval shapes to maximize their color and clarity. They are often set in gold or platinum and used as the centrepiece of a piece of jewellery, such as a ring or necklace. They can also be used in combination with other gems, such as diamonds, to create intricate and beautiful designs.
• Rose Cut - A flat based cut for a preious stone, leaving the surface covered with triangular facets, usually 24 in total.
  
  It was introduced in the 15th century and popular during the 16th and 17th centuries.
  
  The rose cut was the most popular form of diamond cut until the discovery of the brilliant cut at the end of the 17th century, after which its use declined.

This item has been included into following indexes:

• brooches, depicting - butterfly 240
• brooches, diamond - diamond and emeralds 209