Category Archives: Diamond Education

Colour Grade

Diamonds are valued by how closely they are to colourless – the less colour, the higher the value (with the exception of fancy colours ie pink, blue). Most diamonds found in chain jewellery stores contain a slight to significant tint of yellow or brown. Diamonds sold in higher class stores usually range from colourless, to near colourless.

The scale begins with the letter D, representing colourless, and continues with increasing presence of colour to the letter Z. Diamonds are colour-graded by comparing them to stones of known colour under controlled lighting and precise viewing conditions.

Many of these colour distinctions are so subtle that they are invisible to the untrained eye. But these slight differences make a very big difference in diamond quality and price.

Global Diamond’s Tip

We recommend purchasing a diamond between the grades of D (colourless) to G (Near colourless). Any diamond graded either “I” or above starts to have prominent signs of yellow coming from the diamond. These yellowing diamonds should be far cheaper than a diamond with a better colour grade, but they don’t have the same beautiful look.  Sacrifice a bit of size for a better colour grade.

Also note that you cant spend too much money on getting the perfect colour. D coloured diamonds are truly amazing. However if you cant quite afford a D coloured diamond but still want an amazing look, we tend to recommend F colour diamonds for the slightly more price conscious, who still want an amazing look.

Category: Diamond Education

Clarity Grade

It’s all about what you can’t see

By the nature of their formation in the earth, most diamonds contain unique imperfections called inclusions. Diamonds with very few inclusions are rare and, of course, rarity affects a diamond’s value. Using a grading system, diamonds are given a clarity grade that ranges from flawless (FL) to prominent inclusions (I2). Every diamond is unique, but none are absolutely perfect. In determining a clarity grade, diamond graders consider the size, nature, position, colour, and quantity of clarity characteristics visible under 10x magnification.

Common Mistake

Often a first time buyer will mistaken the word clarity for a diamond’s sparkle and radiance. These elements are determined by the diamond’s cut.

Global Diamonds’ Tip:

In general, any diamond with a clarity grade of I1-I3, has inclusions visible to the naked eye. Global diamonds recommends avoiding diamonds in this scale, and advises to purchase in the SI2 grade or higher.

However further to this, a flawless diamond is not necessarily any more beautiful to the eye than an SI2.  For this reason, clarity is a grade you can keep down in the SI grades putting your budget towards other elements of the diamond such as better colour or cut.

Also note that grading for clarity is a subjective matter.  We see many diamonds that say they are SI2, but on inspection they actually look more like I1 grade.  This is where it is important to know that the seller of the diamond actually has the diamond in hand, or is willing to get it in from offshore, without any down payments.  You don’t want to end up with a diamond with inclusions that are visible to the naked eye.

Category: Diamond Education

Carat Weight

Diamonds and other gemstones are weighed using metric carats with one carat weighing about 0.2 grams. It is important to note that two diamonds of equal weight can have very different price values depending on the other characteristics of a diamond’s 5Cs: clarity, colour, cut, and crystal structure.

Global Diamond’s tip:

Never sacrifice quality for size. There is nothing worse than your partner having to continually tell her friends that her diamond doesn’t sparkle because it needs a clean. A diamond with great fire and sparkle will look visibly larger to the eye than a diamond with no lustre. A diamond’s size should be the last piece of the puzzle. Once you have chosen the right grades for yourself, the size of the diamond should be dictated by the budget you have set.

We have also had clients say they saw a 1.00 carat diamond that looked a lot bigger than another 1.00 carat diamond. What this simply means is that the particular diamond was cut with a very wide table, but a very shallow depth. This type of cut may make the actual diamond size look big, but the poor cut proportions will make the diamond look dull and lifeless. It is far better to have a diamond that is cut properly to the correct proportions, as this gives the diamond life and fire.

Another very important issue to note with carat weight is when jewellers talk about total carat weight. This is the total weight of all diamonds within the piece of jewellery. It should be strongly noted that diamonds go up exponentially in value the bigger they get.  Therefore, several small diamonds that make up a 1.00 carat total are far less valuable than one large diamond that weighs the same amount.

Category: Diamond Education

Crystal Structure

There is a “5th C” of diamonds seldom discussed, but very important to understand before making any diamond purchase. This is called “Crystal structure”

Not all diamonds have the same quality crystal structure. This means that two diamonds with exactly the same grades may have a completely different look and value. A poor crystal structure leaves a diamond looking milky and lifeless, even if the other 4 grades (4 C’s) of the diamond show good quality. A diamond with a very good crystal structure will have transparency through the stone, making it look full of life and beautiful.

The issue for the consumer is that there is no accounting for crystal structure within a diamond grading report. It is up to the individual to recognise the difference, or use an experienced and reputable company from whom to purchase.

We are beginning to see more and more diamonds enter the jewellery market that should have been rejected and used in the industrial product market (remember poor quality diamonds are used for industry tools such as grinding disks etc.)
How does this effect your purchasing decision?

It does so in two ways

1. When buying online, make sure you are buying from a supplier who has physically seen all the diamonds being sold in their database. Try to avoid merchants who list from a simple global database. A global database is a listing of diamonds for sale from diamond suppliers around the world. The point here is, even the most experienced diamond salesman cannot guarantee the crystal structure of a diamond if he/she has not seen it themselves. Never pay a deposit or buy a diamond from a merchant without seeing the diamond in the country first.

2. Never buy a diamond from a classic “Trade-me” type seller who has limited diamond knowledge or access. Unfortunately, through lack of experience, these sellers often find themselves associated with suppliers of industrial diamonds. These suppliers are now finding it more financially rewarding to sell their industrial grade diamonds in jewellery sets to E-bay and Trademe stores alike.

When purchasing from Global Diamonds, you are using our experience and reputation to ensure you only purchase a diamond with excellent crystal structure.

Fluorescence in Diamonds – What does this effect?

“Those diamonds that produce a visible reaction when exposed to ultraviolet radiation. In laboratory experiments with both trained gemologists and individuals with no diamond experience (meant to represent the jewellery-buying public), no relationship was found between fluorescence and a diamond’s overall appearance. Diamonds with a strong or very strong fluorescence are a better value for the end customer because the market prices them slightly lower than diamonds with faint or negligible fluorescence”.

So What Does that mean for My Diamond……

Fluorescence is a greatly misunderstood concept. Fluorescence is the reaction of trace minerals within the diamond that cause the diamond to glow when exposed to ultraviolet light. In the laboratory, special ultraviolet lamps are used to check for this but the sun is also a source of ultraviolet rays so diamonds will react in daylight as well. About one third of all diamonds fluoresce. Of these, the most common color is blue, but diamonds can fluoresce other colors. More than 95% of those that do fluoresce will fluoresce blue. The next most common color is yellow. Any other color of fluorescence would be rare.

There are some educational sites or selling sites that discuss fluorescence as a negative value factor. When a diamond fluoresces blue it has a tendency to appear higher in color than its true body color. This is a good thing. However, many years ago, fluorescence was thought to be a negative, and the reasons can only be speculative. One such reason was that it was thought that perhaps the color grade assigned was lower than its apparent color, so people were fearful that they would be paying too much for a diamond. For example, a J color diamond might look like an H or an I color if it had fluorescence. But as long as the diamond is correctly graded as J, then the fluorescence is really like a bonus. The diamond looks higher in color than the price suggests.

Two factors should be considered regarding fluorescence. The first is the color of the fluorescence. If the diamond fluoresces blue, it may be a positive factor since it will make the diamond look whiter. However, note that there is still a stigma against fluorescence and some people will simply not buy the diamond and some sellers will offer a discount for fluorescent diamonds in the higher colors. If the diamond fluoresces yellow, this is a negative factor because the diamond will look lower in color in ultraviolet light.

The second factor is the strength of fluorescence. The range of strengths as reported on laboratory grading reports is None, Faint, Medium, Strong, Very strong (As shown below). Some labs use the term Negligible for any diamond with no fluorescence or faint fluorescence. Sometimes when a diamond has very strong fluorescence, the diamond will have an “oily” look to it, even in normal lighting conditions. When this happens, a negative value is expected. The range of discounts that might be realized are anywhere from 0% to 15%, but a large discount is rare. Occasionally, a slight premium of 1% to 3% might be added for a diamond that is in the lower color grades but exhibits fluorescence.


If you have any further questions about Fluorescence or any other Diamond matters please reply to this blog or contact us through the Contact Us tab and Get in Touch.