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ask-a-goldsmith · 1 month

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In writing my last few posts, I have realized that there is quite a lot of basic(to me) knowledge required to understand most of this stuff. I've done my best to explain as I go, but I think this deserves its own post. So, here we go!

Junior Gemology 101

This post is mostly about diamonds! I am well aware it's called Junior Gemology, but 90% of what I deal with on a day-to-day basis is diamonds. Also, a lot of this applies to coloured stones too, so no need to repeat myself.

What is a diamond, actually?

Diamonds are carbon! That's all there is! Except for inclusions. And coloured diamonds. Those have little bits of other materials in them. And are also a topic for later. I digress. Like always.

Specifically, diamonds are carbon atoms bonded together covalently in a tetrahedral shape. Confusing enough yet? This means that each carbon atom is bonded to 4 other carbon atoms. It's ok if you don't get it, I spent about 3 hours trying to understand diamond structure before things started to make sense. This website has a 3D model of the tetrahedral structure seen in diamonds and is what I used to finally wrap my head around it. The important part is: diamonds are made of carbon atoms connected in a pattern. If the pattern was different, It wouldn't be a diamond! If the carbon was bonded in hexagonal rings, it would be graphite! Same atoms, veeeerrrryyy different result.

What makes diamonds so darn special?

I've told you what a diamond is - so why do people care about this very specific pattern of carbon? The answer is(mostly) that humanity LOVES shiny things, and diamonds are great at being shiny. Why have diamonds become THE shiny thing to have? A combination of some REALLY successful marketing campaigns and some of diamond's unique characteristics. These characteristics include things such as their hardness, brilliance, and fire. I went deeper into these characteristics and what they mean in terms of telling diamonds from other stones in this post, but I'll give you a quick run-down here.

Diamonds are very(and famously) hard. They're a 10 on the Mohs scale, and almost nothing is harder than them. This doesn't mean diamonds are impervious to damage - while they are very hard, diamonds can also be brittle, and a hard smack in the wrong place can chip, crack, or even shatter a diamond. Trust me, I know. I've broken a few by accident.

Brilliance and fire are what give diamonds their characteristic bling. Though they are classified as different things - brilliance being the bright white reflections of light and fire being the rainbow reflections - they're both caused by diamond's Refractive Index. Refractive index(RI) is the measurement of the speed at which light travels through different materials - for our purposes though, think of it as how much a ray of light bends when it moves from one material to another. Diamonds have an RI of 2.42, which causes high brilliance and a medium amount of fire. RI isn't super important for most people to know - it really only comes into the conversation when comparing diamonds to simulant materials.

What are the 4 Cs?

The 4 Cs are the meat and potatoes of diamond basics - Carat weight, Colour, Clarity, and Cut. These four terms are used to describe diamonds worldwide, each describing a different part of a diamond's look.

Carat weight is the weight of a diamond. Pretty self-explanatory. What's not clear is what a carat actually is - no, not a carrot. A carat. A carat is 0.2 grams. Therefore, a 5 carat diamond(good lord) would weigh 1 gram. With me? Why do we weigh diamonds in carats instead of grams like sane people? Because way back yonder, carob seeds were used as a counterweight to weigh diamonds, and language did what language does.

Image from loosegrowndiamond.com

Colour refers to - you guessed it - the colour of the diamond. There are two basic systems that GIA(The Gemological Institute Of America, and the accepted authority of these things in North America) use; the normal colour range and the coloured or fancy diamond range. The normal colour range is used for stones that are colourless, light yellow, or light brown. These are the most common colours of diamond, thus the "normal" colour range. These stones are graded alphabetically D-Z, with D being colourless and Z being quite noticeably yellow or brown. Normal range colour grades are sorted into 5 groups based on the general amount of colour; colourless(DEF), nearly colourless(GHIJ), Faint(KLM), Very Light(N-R), and light(S-Z).

Image from GIA article 4Cs Color

Stones that fall outside this range (stones that are too yellow or brown for the scale or show any colour other than yellow and brown) are graded using the fancy colour grades. Fancy colour grades are an entire thing, but generally pretty self-explanatory. The grade will include 1 or two colours(the more dominant of which goes last) and an intensity descriptor such as light, intense, fancy deep, etc. For example, a stone may be graded as a fancy greyish blue - this means that the stone has a middling amount of colour and is blue with a hint of grey. Easy peasy.

Clarity is how many inclusions are in a stone. Well, technically it's more complicated than that, accounting for placement and contrast and type of inclusion etc etc etc. Really, clarity is how many inclusions you see in a stone. Inclusions are things in the diamond that are not diamond, such as included crystals, or imperfections in the diamond itself, such as cracks(called feathers) or chips.

Clarity grades are, frankly, confusing as fuck. There are 11 grades, broken down into 6 grade groups. From highest to lowest, they are; Flawless, Internally Flawless, Very Very Slightly Included(VVS), Very Slightly Included(VS), Slightly Included(SI), and Included(I). VVS, VS, and SI are each broken into 2 grades - 1 and 2. I is broken down into 3 grades - 1, 2, and 3. The lower the number within a grade, the better the grade - a VS1 stone would be less visibly included than a VS2. You know what'll help? Visuals!!

Images from GIA D&DG Chapter 11. Credit to John Koivula/GIA

The diamond on the left is graded as a VVS2 - the red arrow points to the inclusion that gave it this grade. The diamond on the right is graded as an I2. No red arrows are required - this stone has many highly visible inclusions. If you want a little more info (and examples) of clarity grades, GIA has a lovely little tool that explains it quite well.

Cut refers to the shape of a diamond - specifically, the combination of shape(face-up outline) and cutting style(the arrangement of the facets). A classic round brilliant is what most people think of when they think of a diamond, but there are dozens of different cuts. When talking about cut grade, cut refers to how well executed the cut is. Are the proportions ideal? Is everything symmetrical? Is the polish well done? These determine the cut grade of the stone. Cut grades are as follows, best to worst; Excellent, Very Good, Good, Fair, and Poor.

What are the parts of a cut diamond?

Specifically, the parts of a round brilliant diamond. Round brilliant is the name of the most common cut of diamond. Think of a diamond. Is it round? That's almost definitely a round brilliant. Think I've said round brilliant enough? Round brilliant. Whew. Done with that now. This is best explained with diagrams.

The parts we're most interested in are the table, crown, girdle, and pavilion. The way those 3 parts are shaped and proportioned has a huge effect on the looks and value of a diamond.

Knowledge Check

Let's say you're looking at a 1.01 carat round brilliant diamond - it has a colour grade of F, a clarity grade of SI1, and an excellent cut grade. So, what does this mean to you?

Round brilliant is the cut of the diamond. It has a round outline and a brilliant cutting style. 1.01ct is a fairly large diamond - this one in particular is 6.42 mm in diameter (that's a quarter inch!). This stone is colourless - F is the lowest colour grade in the colourless range, but it is still classified as colourless. The diamond will either have one large or several small inclusions that are easy to see under 10x magnification, but hard or impossible to see while looking through the table of a stone with the naked eye(they may be visible through the pavilion with the naked eye). The diamond will be very well cut - the best cut grade possible, in fact! There will be no visible variation in the girdle outline, and all the facets will be well-placed and symmetrical.

It's up to you to decide if this stone matches your criteria - is SI1 a good enough cut grade for you? Is 1.01ct the right size? How "good" a stone is depends on what you want - there will always be bigger, clearer, more colourless diamonds on the market. What makes a stone "good" is if it's the right fit for you. Another stone may be better quality, but if it's out of your price range, then it's not a good stone for you.

In Conclusion

So, you made it this far! Congrats! Hopefully, I haven't bored you too much. We've really just scratched the surface - this was enough information to give you a good idea of what's going on and allow you to navigate the mysticisms of those strange numbers and letters you see associated with diamonds. All information was taken from the GIA Diamond Essentials 130 and Diamonds and Diamond Grading 230 courses and my 6ish years in the jewelry industry. If you have questions about specific pieces of information or want more resources, send me an ask! I will be delighted to answer.

#WOW this on is an absolute beast #final word count is 1674 #fun fact this is how i'm studying for my gemology final #long post #goldsmith answers

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