Opal and Diamond Victorian Crescent Brooch

• 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.
• Victorian Period - The Victorian period of furniture and decorative arts design covers the reign of Queen Victoria from 1837 to 1901. There was not one dominant style of furniture in the Victorian period. Designers used and modified many historical styles such as Gothic, Tudor, Elizabethan, English Rococo, Neoclassical and others, although use of some styles, such as English Rococo and Gothic tended to dominate the furniture manufacture of the period.
  
  The Victorian period was preceded by the Regency and William IV periods, and followed by the Edwardian period, named for Edward VII (1841 ? 1910) who was King of the United Kingdom and the British Dominions and Emperor of India for the brief period from 1901 until his death in 1910.

This item has been included into following indexes:

• brooches, crescent - crescent, with diamonds 87
• brooches, depicting - crescent moon 221
• brooches, set with - opal with diamonds 120