Diamond (from Ancient Greek άθραυστος "unbreakable/indestructible") is the metastable allotrope of carbon whereby the carbon atoms are arranged in a variation of lattice-diamond structures giving it the highest hardness of any known natural bulk material.
They have remarkable optical characteristics. Because of its extremely rigid lattice, it can be contaminated by very few impurities such as nitrogen. Combined with wide transparency, this results in a natural diamonds clear, colourless appearance. Diamonds brown, blue, green, orange, red, pink and black also exist, in their rarities.
Diamonds have a hardness of 10 on the Mohs scale of mineral hardness (10 being the hardest, 1 being the softest). Only diamond can cut diamond and is therefore the main property of any industrial application or tool. Diamonds worn in ancient times were believed to promote strength, invincibility and courage.
-THE FOUR C's-
In 1940s, GIA established the "4Cs" and the International Diamond Grading System™ – to this day, the worldwide standard for evaluating diamond quality.
Diamonds in the D-to-Z colour range are valued by how closely they approach colourless. The less colour, the higher their value.
The absence of inclusions and blemishes makes a diamond rare and affects value.
The sparkle and brilliance of a diamond depends more on its cut than anything else.
Diamonds and gemstones are weighed in metric carats: one carat is equal to 0.2 grams.