Price Guide to Antiques & Collectables
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Tanzanite and Diamond Polygonal Ring

18ct white gold, tanzanite, diamond and onyx ring, of open work polygonal design centring a pear-shaped tanzanite bordered by pave-set brilliant-cut diamond and polished onyx surrounds accented by baguette diamonds, the tanzanite and diamonds together weighing approximately 5.75 carats and 0.81 carat respectively, size L½.

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  • 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.
  • Openwork in Jewellery - Openwork, also known as pierced work, is a decorative technique used in jewellery making that involves removing or cutting out sections of metal from a piece of jewellery to create a pattern or design. This technique can be used in a wide range of jewellery styles, including necklaces, bracelets, earrings, and rings.

    Openwork jewellery can be made using a variety of different techniques, including hand carving, sawing, and laser cutting. The design can be simple or complex, and can feature a range of different shapes and motifs, from delicate floral patterns to bold geometric designs.

    One of the advantages of openwork jewellery is that it can add visual interest and depth to a piece without adding a lot of weight or bulk. This can be particularly appealing in larger pieces, such as necklaces and bracelets, where heavy materials can be uncomfortable to wear.
  • 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.

This item has been included into following indexes:

18ct white gold, tanzanite, diamond and onyx ring, of open work…