Dimanti ir reti, skaisti, dārgi. Viņi ir "meiteņu labākie draugi" un (ne tikai) zēnu labie ieguldījumi. Šeit ir pārskats par to, kas mums būtu jāzina par dimantiem, lai izdarītu pareizo izvēli neatkarīgi no mūsu mērķa. Trešajā daļā dimanti ir aprakstīti detaļās*
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Gabriel Levin-Cafrir (M.Soc.Sci), second generation diamantaire, graduate of the Center of Gemological Studies under the leadership of one of the leading Graduate Gemologists of Israel - Eli Dori, specialization - Diamond Expert (“Diamond Grading & Evaluating” diploma), at Diamond Exchange, Ramat Gan, Israel. The evaluation of diamonds is based on the G.I.A (Gemological Institute of America) standards. Practiced in Israeli commpany “Keren Or”. Works in jewellery and gemstones sales sphere (family business), consults, does lecturing.
Detailed About Diamonds
Diamond Hardness
Diamond is the hardest material on earth: according to GIA researchers, diamonds are 58 times harder than anything else in nature! Can you believe it? But it is a reality. But there is small secretI want you to know.
According to “Mohs scale” (qualitative ordinal scale characterizing scratch resistance of minerals) invented by German geologist and mineralogist Friedrich Mohs, diamond hardness is graded by 10 out of 10 – the maximum possible. Yes, diamond is the hardest, but not the most durable!Let’s see what the difference is.
Hardness – is the ability of a material to resist deformation, which is determined by a standard test where the surface resistance to indentation (by another indenter - hard material) is measured (https://www.sciencedirect.com/topics/engineering/hardness). Another words, hardness is resistance to wear and tear, due to external force. Hardness often is related to object’s surface.
Durability – is the ability of structures and their constituent elements to resist destruction under the influence of external loads (such as forces, pressures) (https://isopromat.ru/glossary/prochnost). Durability is ability of withstanding that force and other forces and the object remain whole. Durability considers object as a whole.
So, if inside a diamond there is at least one small crack, putting a force on this spot will get the diamond destroyed – cracked into pieces (two minimum). It happens because of the inside pressure directing to surface. When pressure from inside and outside meets, they break the stone. That is why especially jewelers have to be very patient and careful while putting diamonds inside jewellery. In my experience I have several cases of broken melee diamond (small diamonds weighting not more than 0.2 ct).
As you see, even with diamond we have to be careful. A diamond is forever, as De Beers once declared, but it is also in our hands to make it stay like this.
Diamond Types
“We produce IIa type diamonds,….” – this kind of statement you may have seen in some advertisements of laboratory-grown diamonds (this, for example, https://www.youtube.com/watch?v=YzkS7rXSkS0). But have you ever thought about “IIatype” meaning, why it is so special and what are the other types and why they are not so special etc.? Now this question will be cleared.
As we discussed earlier, pure diamond is made of only one element: carbon. The atoms are arranged in a regular repeating pattern (the diamond lattice) that is unique among gems. However, atoms of elements such as nitrogen and boron can replace some of the carbon atoms in the lattice. And this gives us the foundation of the type classification system - the presence or absence of nitrogen (the most common impurity in diamond) and boron, and the ways in which they are arranged in the lattice.
There are two main types: “I” and “II” (presence or absence of nitrogen). Each type has two more subtypes (according to the arrangement of nitrogen atoms - isolated or aggregate, and the occurrence of boron impurities): for “I” type – “Ia” and “Ib”; for “II” type – “IIa” and “IIb”. So, overall there are four groups: Ia, Ib, IIa, and IIb(from “The type classification system of diamonds and its importance in gemology” by Christopher M. Breeding and James E. Shigley).
- Type I diamonds are defined as containing sufficient N to be measurable by IR absorption spectroscopy.
- In type Ia diamonds contain nitrogen atoms that are in close proximity to one another in one of two spectroscopically detectable configurations.
- In type Ib diamonds, single nitrogen atoms that have replaced carbon atoms in the lattice are isolated from one another; that is, they generally do not occur in adjacent lattice positions.
- Type II diamonds do not contain enough N to be detected by the IR spectrometer.
- In type IIa diamonds contain no easily measurable N or boron impurities.
- In natural type IIb diamonds likewise contain no IR-measurable N impurities, instead, type IIb diamonds contain boron impurities that are thought to be isolated single atoms that replace carbon in the diamond lattice.
As you see, the “IIa” type diamonds is the purest diamonds from all, and as a result most desirable. That is why those, who produce IIa type diamonds underline this criteria. Now you know
Diamond Grading
I assume you have heard that diamonds are grade by the special and unique system that is called “4C’s”. Just to remind, 4C’s stands for:
- colour - the degree of absence of colour if the diamond is considered colourless; the degree of colour saturation if it is “Fancy Coloured”,
- clarity - the degree of impurities that are in diamond,
- cut - the degree of how well diamond is cut,
- carat weight - the actual weight of stone in carats, 1 ct = 0,2 gr.
Those are the most important characteristics of a diamond my colleagues and I as diamantaire and diamond gemologist look for to put a grade, diamond cutters – use these systems’ parameters in cutting process, clients – value and desire so much.
The system was invented in the early 1940s by a former retail jeweler and then GIA founder Robert M. Shipley, and then developed, all diamond grading laboratories accepted the system and started to grade diamonds accordingly. Nowadays we can’t even imagine a diamond grading report without the 4C’s system. Maybe someday a new method will be found, but is it needed? We shall see.
What I can say is that now tech.companies invent new devices that grade diamonds using the 4C’s system to more and more eliminate the “human presence” in grading and evaluating processes.What professional do is bringing intuition and experience into the diamond grading process. Yes, there is no doubt that machine can put a correct stamp on a gem and call it a day. But only a person can unlock the true potential of a diamond and tell the story hidden inside.
Diamond Fluorescence
Fluorescence is diamond’s reaction to long wave UV rays. Another words, fluorescence is the visible light some diamonds emit only when they are exposed to invisible ultraviolet rays (which is an essential component of daylight) that gives a glowing effect.
This effect occurs because of submicroscopic substitutions and/or shifts in the diamond structure. By the way, that substitutions can either cause fluorescence or prevent it. The majority of diamonds do not fluoresce, but those that does - in more than 95% cases, the colour is blue. In rare instances, the reaction is orangy yellow, yellow, orange, red, white and green.
A diamond’s fluorescence is graded by its intensity: None, Faint, Medium, Strong and Very Strong. Sometimes I know that the fluorescence appears in a diamond by seeing the “bluish effect” under the white light through the “crown”, but only if it is “strong” to “very strong”. Fluorescence doesn’t mean that a diamond with it is better than the diamond without that effect or other way around, let’s say it is an extra that a stone has. So from the customers’ point of view fluorescence is and should be a matter of taste, nothing more.
A relevant question about the fluorescence can be: does fluorescence means the diamond is a natural diamond and not substitute? And the answer is – no. Firstly, as we discussed previously, not all natural diamonds fluoresce. Secondly, some lab-grown diamonds do fluoresce. Finally, some materials like cubic zirconia can display fluorescence.