A brief guide to diamonds and the 4 C's

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What is the meaning of carat?

Apart from not being a vegetable, the word carat has two distinct meanings. In relation to gold, carat refers to the purity of the metal e.g. 24 carat (pure gold) or 18 carat etc, also written as ct or in many countries as karat or k.(more on precious metals at bottom of page) 

In relation to gemstones  especially diamonds, carat is a measurement of weight. One carat is 0.2 grams, a carat can be split into 100 points, therefore a half carat diamond may be described as a 50 point stone, and this would weigh 0.1 grams. Carat is often mistaken for size, and although it is usually possible to determine the approximate carat or weight of say, a good brilliant cut diamond by its diameter, an old cut, (antique cut) or poorly cut stone is much harder to guess by size alone, as the different facets may be cut in a variety of ways and depths.

What is a good quality diamond?

Diamonds are graded by what is commonly known as the 4 C's: carat. colour, clarity, and cut.

The higher the grade in each category the higher the price.

The weight or  carat of a diamond will usually be the dominant factor in the price, but the other factors are also extremely important.

The most desired colour of a diamond is described as 'exceptional white' unless it can be described as a 'fancy' coloured diamond. An indistinct yellow or brown could not be described as a fancy coloured diamond, but rather as a lower grade white diamond. Colours are graded from D (exeptional white or colourless) down to V (yellow or strongly tinted).

Clarity, or the prevelance of inclusions (popularly called flaws), is graded from IF (internally flawless) down to P3 or pique 3 (large clearly visible inclusions).

The cut may be described as from very good to poor. The way the diamond is cut is very important to the overall balance of the stone and the way the facets allow the light to pass into the diamond and to be reflected back to the top. A poorly cut diamond may have irregular facets and be cut too deep this will result in a higher caratage but at the expense of diameter (or the spread), and the brilliance.

Taking these factors into account Welded Bliss would consider a good diamond to have a colour of minimum 'rare white' or 'white', grade G to H. The clarity minimum SI (eye clean, small inclusions only visible under 10 x magnification.

What are conflict diamonds?

Conflict diamonds are diamonds which have been illegally traded, mainly from West Africa, often for weapons. The trade in these diamonds has fuelled war and, social and political instability in this region. A reputable retailer or manufacturer will use diamonds from merchants who can prove a chain of supply which does not involve conflict diamonds. 

More on Precious Metals

As mentioned above 24 carat gold is pure gold which can also be expressed as 1000 (parts) or 100% pure.
18 carat gold is an alloy of gold and other metals, most notably silver and can be expressed as 750 (parts) or 75% pure. 9 carat gold is an alloy of gold and other metals, primarily silver and can be expressed as 375 (parts) or 37.5% pure. At 9 carat purity you could be forgiven for thinking that the resultant metal alloy can not be called gold when it contains well under half of the precious metal it is named after, but as long as you understand the content of the metal you are purchasing then there should be no problem with this traditional way of describing the alloy.
24 carat gold is usually considered to soft or malleable to make practical jewellery in most cases, which is the main reason it is alloyed with other metals. The other reasons apart from physical working properties are, Price and Colour. 
As gold (pure gold) is always yellow hued, in order to create white or red (rose) gold it would always have to be alloyed with other metals. Red gold obtains its colour through copper alloying and white gold through combinations of silver, palladium or perhaps other platinum group metals. Nickel is no longer used in commercial production in the West. A further way of colouring gold is through plating which does not change the carat of the gold as the metal content is minimal. It is common to Rhodium plate white gold in order to give it a lighter hue.
As a consumer you should expect to know if an item has a plated finish as it affects the look of a finished item and the finish will deteriorate over time. It is your choice if you prefer this finish but you should make an informed decision.

For Silver the same applies, 1000 (parts) or 100% pure is used less frequently.
The most common standard is 925 (parts) or 92.5% pure and this is known as Sterling Silver.
Sterling Silver is the standard which was coined (literally) in England approximately 600 years ago and today has been adopted throughout the world. 

Modern minimum standards in the UK for a metal to be called silver is 800 (parts) 80% pure.
For gold it is 9 carat or 375 (parts) 37.5% pure.

Other precious metals which are hallmarkable in the UK are Platinum and Palladium.

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