Diamond introduction
Diamonds
Education and introduction.
In selecting a diamond, the rarity, value and beauty is determined by the four factors mentioned above, called the 4C's: Carat Weight, Color, Clarity, and Cut (proportions & finish).
Carat Weight
Carat weight refers to the size of the diamond. Based on a standard unit of measure, one carat is divided into 100 points. The term originated from carob seeds that were used to balance scales in ancient times. Learn more
Color
The most desirable diamonds are colorless because the absence of color enhances the diamond's ability to reflect a rainbow of color. Diamonds are graded on a scale of D (almost clear white) to N-Z. Learn more
Clarity
Diamonds can contain slight imperfections. Often invisible to the naked eye, these natural birthmarks fall into two categories-inclusions (internal) and blemishes (external). Fewer inclusions increase the value of the stone. Learn more
Cut
Cut gives the diamond its brilliance. Of the four C's, it's the only one dependent on a human touch. Using precise mathematical formulas, the cutter transforms a diamond in the rough into a sparkling jewel that reflects and refracts light. Learn more
Diamond glossary term and definitions Download
The formation of natural diamond requires very specific conditions—exposure of carbon-bearing materials to high pressure, ranging approximately between 45 and 60 kilobars (4.5 and 6 GPa), but at a comparatively low temperature range between approximately 900–1300 °C. These conditions are met in two places on Earth; in the lithospheric mantle below relatively stable continental plates, and at the site of a meteorite strike.
The conditions for diamond formation to happen in the lithospheric mantle occur at considerable depth corresponding to the requirements of temperature and pressure. These depths are estimated between 140 and 190 km though occasionally diamonds have crystallized at depths about 300 km as well. The rate at which temperature changes with increasing depth into the Earth varies greatly in different parts of the Earth. In particular, under oceanic plates the temperature rises more quickly with depth, beyond the range required for diamond formation at the depth required. The correct combination of temperature and pressure is only found in the thick, ancient, and stable parts of continental plates where regions of lithosphere known as cratons exist. Long residence in the cratonic lithosphere allows diamond crystals to grow larger.
