What You Need to Know

Let's first start with the diamond part of the diamond engagement ring (as it's the largest component by far of the cost). The geological process that forms a diamond happens in only rare circumstances. Diamonds are formed from carbon atoms between 100km and 200km beneath the earth's surface under specific temperatures and pressures. Diamond's are carried to the surface by volcanic eruptions. Because of the rare circumstances around their creation, larger diamonds are uncovered much less frequently than smaller ones. For this reason the price of diamonds rises exponentially as its size increases

Loose diamonds are rated based on the “Four C's”. They are ‘Cut', ‘Color', ‘Clarity' and ‘Carat'. These four criteria are the most important things you need to be aware of when purchasing a diamond. Luckily – all four criteria are rated using standard scales, which makes purchasing a diamond online easier as the diamond is not subject to ambiguity. The Four C's are all instrumental in a diamond's selling price is determined and how an engagement ring looks.

Let's briefly talk about the Four C's:

Diamond Carat Weight:

A carat is a unit of measurement used to weigh a diamond. One carat is equal to 200 milligrams, or 0.2 grams. I gave my fiancé a 1 carat diamond, which is a nice size for those of us who don't have a Donald Trump bankroll (incidentally Donald Trump purchased his fiancé a 14 carat diamond worth over 1.5 million). A couple things to note – don't confuse ‘carat' with ‘karat', which is a measure of the purity of gold. Also, from my experience the carat weight is the most important of the Four C's in terms of making an impression on your fiancé (As long as the other 3 C's are adequate [more on this below] ). When buying a diamond engagement ring be sure to compare prices based on the per carat value of the diamond. All other C's being equal (or close to equal), this is a great way to compare diamonds.

For example if you were looking at a (a) 1.67 carat diamond that was $3,407, a (b) 0.58 for $1,230 and a (c) 1.08 carat diamond for $2,689 you could, assuming their clarity, colorand cut were similar, compare them on a per carat basis as follows:

(a) $3,407 / 1.67 = $2040.10 per carat

(b) $1,230 / 0.58 = $2120.69 per carat

(c) $2,689 / 1.08 = $2489.81 per carat

Right about now is a good time to warn you about a marketing scam some diamond vendor's try to use. It's called “Total Carat Weight (TCW)” and can also appear as “Carat Weight Total”, “CWT” or “Ct. TW”. What this is in reality is the total weight of ALL the diamonds on the engagement ring. In other words you may have a 1 carat center diamond and four 0.1 carat smaller diamonds on the engagement ring band. This engagement ring with have a “Total Carat Weight” of 1.4 carats. Vendors may try to trick you into thinking that the center (main) diamond is 1.4 carats and will jack up the price accordingly.

FYI – The word ‘carat' is derived from carob seeds that were used historically to balance scales. Carobs are so uniform in shape and weight that they were used for this purpose.

FYI – Diamonds usually significantly increase in price in per half carat or quarter carat intervals such as 1.0, 1.25, 1.5. So one strategy is to purchase a diamond very slightly under the weight you want (you won't notice the difference). For example if you want to buy a 1 carat diamond go for a 0.97 carat one instead and see how much you save!

Diamond Color:

Diamonds range in color between clear to yellow. Generally clear diamonds are regarded to be the best. Certain types of yellow diamonds, however, are very valuable because they can be quite rare. The classic diamond (the one your GF will want) should be clear.

There are two color scales used to evaluate diamond color, the GIA and AGS (GIA is used by most retailers). A table below shows how jewelers rate diamond color

Based on the GIA ratings for color you ideally want a diamond that's H or above. A diamond with the clearest ratings (D, E, F) are generally extremely expensive and rare, whereas anything worse than an J will start to appear visibly yellow. Most people opt for G, H or I. Anything worse than M belongs in costume jewelry. There is a trick that some retailers use (that you won't have to worry about when buying online). They place the diamond on a black surface – this makes even the yellowishdiamonds appear clear. If your buying from a retailer be sure to always view the diamond on a true white background.

Another aspect of diamond color is fluorescence. This is the diamonds reaction to ultraviolet light. This is the deal with fluorescence: If you have a slightly yellow diamond some fluorescence is good as it will get rid of some of the yellow when looking at the diamond in broad daylight. However, if you have a fairly clear diamond, fluorescence will only make your diamond appear dull in broad daylight. Generally fluorescence in a diamond will reduce its value by 10 - 20%. Retailers may try a gimmick by called a fluorescent diamond a ‘blue-white' diamond (because of the way a fluorescent diamond appears under ultra-violet light). Using this terms is actually illegal by the FTC. So if you see it being used DO NOT BUY FROM THIS RETAILER.

Diamond Cut:

The diamond cut can affect the value of the diamond by up to 50%. The most common engagement ring cut is a round brilliant diamond cut. Other type of cuts include a princess cut, an emerald cut, the asscher cut, the marquise diamond and the brilliant cut. The cut you get is purely a matter of taste (if your woman like the traditional, however, stay with the round brilliant.

The way a diamond is cut is also very important. An ‘ideal cut' means that the diamond is cut to a certain mathematical specification that ensures ideal light reflection and refraction (making the diamond sparkle ‘brilliantly' under light). Ideal cut diamonds usually have a significant premium put on them as they require a lot of work from a gem cutter.

Diamond Clarity:

Most diamonds have naturally occurring internal flaws which are known as inclusions. Inclusions can be small carbon deposits tiny air bubbles, micro cracks and clouds. On a diamonds surface, flaws such as imperfect corners, scratches or pits can occur. Some flaws can be seem with the naked eye and seriously devalue the diamond. Some flaws can only be seen with a 10x loupe (a magnifying glass) and, while making the diamond less expensive, will not be noticeable to your fiancés friends.

There are two standard when it comes to rating diamond clarity – the GIA scale and the AGS scale shown below.

The GIA scale is used more commonly. The VS2, SI1 and SI2 are a good tradeoff between clarity and affordability.

FYI – Retailers might show you ‘Clarity Enhanced Diamonds' which are reworked diamonds that can longer be certified (by GIA as GIA does not certify clarity enhanced diamonds). Clarity enhance diamonds have been ‘fixed' by various means such as laser or fracture filling. I recommend staying away from these as the ‘fixes' may reverse over time