Banded agate and onyx necklace, circa 1940
- 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.
- Onyx - Onyx is a form of agate, used from antiquity and popular again in the 1920s and 30s. European onyx is generally green, but can be many other colours, and can contain bands of black and/or white.
This multicoloured stone is widely used for table tops, lamp bases and in jewellery. Some types of onyx are also used for cameos of which the upper white layer is cut away to reveal the colour beneath.
- 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.
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