Getting to know Diamonds

Diamonds are formed by the transformation of carbon into pure carbon. This process takes billions of years to occur, at very high pressure (at depths of more than 70-150 km) and temperature (over 1300°C).

Only a small quantity of the diamonds extracted from the mines is destined for jewelry, and of this quota only a very few are high quality gems larger than one carat.

Diamond features the highest hardness of any naturally occurring material. On the Mohs scale of mineral hardness (from 1 to 10) it is the hardest (10), followed by corundum (9) that are 140 times less hard.

Another typical property of diamond is its very high refractive index (2.42).

These two features lead non-experts in gemology to confuse diamonds with synthetically produced moissanite (silicon carbide) because it is 35 times harder than corundum and has a refractive index that is higher than that of diamond (2.65).

Moissanite is birefractive (diamond is singly refractive), and this allows experts to distinguish it from look-alikes without the need for gem analysis. The market offers other diamonds with the same hardness (10) and refractive (2.42) indices of natural diamonds. These are synthetically produced in laboratories and are known by special names – CVD, Chemical Vapor Deposition and HPHT, High Pressure High Temperature. They can be distinguished from natural diamonds only when tested using special instruments.

Based on the foregoing, it is best to purchase diamonds from dealers who are experts in gemology, or diamonds that come with gemological testing certificates issued by officially qualified institutes such as GIA, HRD, IGI, etc. that provide a reliable scientific statement of their authenticity. The certification issued by the factory or by the shop keeper is based on trust and, sometimes, cannot be disputed. Gemologist certification is the best guide for purchasing a diamond and is fundamental in establishing its value with certainty.

The gemologist analyses the gem based on the ‘4C’s’:
Carat – Clarity – Color – Cut

Carat (ct.) is the weight metric used for precious gems. One metric carat amounts to two-tenths of a gram and is divided into 100 points (one point is one hundredth of a carat).

Claritythe clarity scale is divided into:
P3 or I3, P2 or I2, P1 or I1 (inclusions visible to the naked eye),
SI2, SI1 (inclusions visible under x10 magnification – barring rare exceptions),
VS2, VS1 (very small inclusions difficult to see under x10 magnification),
VVS2, VVS1 (very very small inclusions difficult to see under x10 magnification),
IF (internally flawless),
FL (flawless both inside and out).

Color in a diamond is determined by the presence of atoms other than carbon that remain trapped in the diamond’s crystal structure during formation. The most common diamonds contain nitrogen atoms that give each diamond its color that can range from colorless to more or less intense yellow/brown tones, based on the distribution of the atoms.

Diamond color grading is made based on the white scale (white diamond):

D, E, F, G, H, I, J, K, L – Z
(the most desirable colours are D, E or F.)

Distinctly colored diamonds, called ‘fancy’, can be found in colors such as blue, green, pink and much more rarely red, in function of the atoms of other elements that are trapped inside them (hydrogen, boron, etc.).

Cut Diamonds can be cut in different ways: round brilliant, oval, emerald, heart, marquise, princess, pear as well as other fancy shapes. The round brilliant diamond cut is the one most commonly seen because it refracts light in the most desirable way. A round cut consists of 56 facets plus the table, distributed between the diamond’s crown and pavilion.

It is very important that the cut be made in compliance with each stone’s ideal proportions so as to guarantee the maximum refraction of light. To achieve greater gains, wholesalers often ask cutters to cut the stones so as to leave the highest weight possible, thereby greatly reducing the correct refraction of light. The comparative scale for refraction found on certificates (excellent, very good, good, fair and poor) makes it easier to choose. The best choices are excellent or very good, and the same applies to polish and symmetry.


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