Diamond “Blood” Types

Types of diamonds illustration
Just like a blood type for humans, diamonds have four distinct groups based on their crystalline structure. Type II stones are the rarest and sought after by connoisseurs and collectors.

Type Ia – diamonds contain clusters of Nitrogen atoms throughout the crystal structure. Those stones usually display some degree of yellow color. Nothing to write home about.

Type Ib – diamonds contain only Nitrogen atoms. These stones are 0.1% of all diamonds with an intense orange, brown, and sometimes green color.

Type IIa –  Type II diamonds have no measurable impurities lack Nitrogen in their crystal structure. They represent less than 2% of all-natural diamonds and are the most valuable. They are characteristically colorless, transparent, and exceptionally white. Colorless IIa diamonds are typically traced to the Golconda mine in India.  Many famous diamonds are classified as Type IIa including the Cullinan Diamond and Koh-i-Noor Diamond. Fancy-colored type IIa diamonds could be pink or purple.

Type IIb – diamonds contain traces of Boron within the crystal. They are those blue or blue/gray diamonds everyone is craving to collect. They represent only 0.1% of diamonds.

  • Type Ia encompasses roughly 98% of natural diamonds. They all have detectable traces of Nitrogen atom clusters. They are the most common type – 98% of all-natural diamonds.
  • Type IIa and Type IIb stones are rare and usually sought after by connoisseurs and collectors.
  • Are all D Flawless diamonds type IIa? Not necessarily, but most likely.
Diamond types type ! and type !! diamonds
India Diamond mines Golconda illustration by Leon Mege

Golconda Diamonds

Two thousand years before diamonds were discovered in Brazil and South Africa, the only source of diamonds in the world came from the Indian mines of Golconda. These famous mines are located near present-day Hyderabad and were named for the 14th-century Indian sultanate.

The “Golconda” designation suggests that the stone’s origin can be traced to the historic mine. However, by the beginning of the 18th century, the mine had exhausted its supply of raw gems.


A disproportionate number of the world’s most famous diamonds came from Golconda; some of them are:

  • The 105.6 carats (186 carats before a butchered attempt at re-cutting in 1852) Koh I Noor diamond adorning the Queen Mary’s crown during her 1911 coronation;
  • The  410 carat Regent diamond – one of the last large diamonds to be found in India;
  • The 70 carat Idol’s Eye, once paid in ransom by the sultan of Kashmir for the release of Princess Rashidah;
  • The 32 carats Agra once adorned the Mughal emperor Babur’s turban;
  • The 31 carats Wittelsbach, pawned to King Philip IV of Spain for the dowry of the Infanta Margarita Teresa
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