Types of Diamonds
Posted on February 13 2014
Most people categorize natural diamonds as either white or fancy colored. People assume that if a diamond is almost entirely made up of the single element carbon, then they are all more or less the same. What people don’t know is that the 1% actually affects the diamond a lot! Diamonds have “types” and these classifications are by level and type of chemical impurities. In other words, the amount and nature of another element in a diamond can make a significant difference on its appearance. There are four diamond types: Type Ia, Type Ib, Type IIa, and Type IIb. Since all diamonds are 99% carbon, it is the last 1% that indicates the diamond type and ultimately what the diamond will look like. All diamonds fall within a type; types are distinguished only on an atomic level using infrared spectrometer, which is performed at all gemological laboratories. Below are some basic facts about the four major diamond types and what kinds of diamonds they produce.
Type I: The most common kind of diamond, this category makes up 98% of all natural diamonds. Type I diamonds are 99% carbon and 1% nitrogen. The presence of nitrogen in diamonds causes a natural yellow color. How the nitrogen atoms are arranged atomically differentiates Type Ia from Type Ib.
Type 1a: Diamonds in this category have nitrogen atoms in pairs. Diamonds in the normal D-Z color range are in this category.
Type 1b: The nitrogen atoms are dispersed throughout the crystal as clusters rather than pairs. The nitrogen clusters produce a very strong yellow or brown color, also known as fancy or ‘canary’ diamonds.
Type II: Diamonds have no measurable amounts of nitrogen atoms. Type II diamonds are extremely rare and command high prices for their colorless nature. These type diamonds form in specific regions of the world and under specific conditions that are distinctly different than the majority of diamond deposits. Type II diamonds are popular among collectors and auction houses for their rarity. These diamonds are different than colorless Type Ia diamonds which do still contain small amounts of nitrogen.
Type IIa: The diamonds have no nitrogen and are colorless. The term “golcanda” refers to a region where Type IIa diamonds have been mined. “Liquid Ice” is gemological jargon often used to describe how these diamonds look when under magnification. Fancy pink diamonds also fall under this category although their color is not attributed to the presence or lack of a single element.
Type IIb: The diamonds have no nitrogen but significant traces of Boron. The element Boron makes the color blue in diamonds. Natural grey and blue diamonds are this diamond type.