Australian Gold Nugget and Agate Brooch, Circa 1860

• 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.
• Agate - Agate is a type of semi-precious gemstone that is made up of silica dioxide, a mineral that is also found in quartz. It is known for its distinctive banded patterns, which are created as layers of silica are deposited in different colours including red, orange, yellow, green, blue, and purple. It is often used in jewellery, decorative objects, and other decorative items, and it is prized for its beauty and durability. Agate is found in many parts of the world, including Brazil, India, and the United States.

This item has been included into following indexes:

• brooches, set with
  • agate 236
  • goldfields nuggets 147
• miners / mining / goldfields - jewellery, brooches, Australian 287