Craton Map of World's Diamond Regions
As diamonds are created under compression from volcanic events the stones originate from kimberlites and dykes. Erosion over time has removed stones from their ore and as a result of this there are large alluvial fields from ancient and current river systems as well in the ocean.
What is a Diamond?
In mineralogy, diamond (derived from the Greek word adamas – meaning unbreakable) is a metastable allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centred cubic crystal structure called a diamond lattice. Diamond is renowned as a material with superlative physical qualities, most of which originate from the strong covalent bonding between its atoms. In particular, diamond has the highest hardness and thermal conductivity of any bulk material.
The Carat System
The modern carat system started with the carob seed. Early gem traders used the small, uniform seeds as counterweights in their balance scales. Some weights are considered "magic sizes" – half carat, three-quarter carat, and carat. Visually, there's little difference between a 0.99 carat diamond and one that weighs a full carat. But the price differences between the two can be significant.