This is an in depth look at diamonds, the 4C's, terminology and much more. This is a two-year gemmology course condensed into a few pages. This will help demystify and unravel the complex technicalities that are diamonds, and the multiple factors that influence the price.
What do rough diamond look like?
Diamond has a cubic crystal structure, specifically known as the diamond cubic structure.
Key details:
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Crystal system: Isometric (cubic)
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Lattice type: Face-centred cubic (FCC) with a two-atom basis
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Space group: Fd-3m
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Coordination: Each carbon atom is tetrahedrally bonded to four other carbon atoms via strong covalent bonds
This highly symmetrical, tightly bonded structure is what gives diamond its exceptional hardness, high refractive index, and thermal conductivity—all critical properties in fine jewellery and gemmology.
In simpler English, a rough well-formed diamond crystal is an octahedron, a mirrored four-sided pyramid on another four-sided pyramid.
Whist the internal molecular structure does not change, the outward appearance can vary from a perfect crystal to a rough looking pebble, you might not look at twice.
Carat Weight
The word Carat was originally derived from the word Carob, as in the Carob seed.
Before the advent and invention of electronics, specifically the diamond scale we relied upon a balance scale. As it happens the weight of the carob seed is very consistent (0.2g) hence, 1 Carob = 1 Carat!
From this the below was created
• 1 Carob = 1 Carat = 0.200 grams
• 1 Carat = 100 points (approx. 6.40mm)
• ½ Carat = 50 points (approx. 5.2mm)
Nowadays we use a slightly more sophisticated weighing system, measuring to three decimal places. ie. 1.000ct
Commercial Reality - Diamonds are priced by weight in dollars per carat, the larger the diamond the higher the price per carat for the same quality. It's important to understand that for the same quality the larger the stone the price per carat can increase exponentially.
