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Diamond Carat Weight


Understanding Diamond Carat Weight


Diamond carat weight serves as a crucial metric measure, defining the weight of a diamond. It is important to note that 1 carat is equivalent to 0.20 grams, and much like a pound is divided into 100 pennies, a carat is divided into 100 points. When referring to a diamond, if it weighs half a carat, it will be expressed as 0.50cts. The carat weight is a key determinant of a diamond's value.

Diamond Carat Weight vs. Physical Size


It's essential not to confuse diamond carat weight with the physical size of the diamond. While it's logical to assume that an increase in carat weight corresponds to a larger diamond, these are distinct characteristics. Carat weight and measurement relate to an increase in the quantity of diamonds, but both remain separate units of measurement—one related to weight and one to size. 


The Origin of Diamond Carat Weight


The term 'Carat' originates in the Greek word for the 'Carab' plant, whose seeds were consistently used to measure weight. Carob seeds weighing nearly 1 carat with minimal variation were employed with balance scales to determine diamond carat weight. Their consistent weight made them a reliable measure in the historical assessment of diamonds.

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Carob seeds, were once used with balance scales 
 to help determine diamond carat weight  


The Origin of the Carob Seed


The carob tree (Ceratonia siliqua), native to the Mediterranean region, has a rich history and diverse applications. Renowned for its distinctive elongated pods, the carob tree has played a significant role in various cultures and continues to find utility in modern times. The carob tree is an evergreen that thrives in warm climates, particularly around the Mediterranean basin. It is well-adapted to arid conditions and can be found in countries such as Spain, Italy, Greece, and parts of the Middle East. 

The tree is characterized by its glossy, leathery leaves and can reach substantial heights. The pods of the carob tree, often referred to as locust beans, are a defining feature. These elongated pods house seeds and taste sweet, contributing to their historical use as a natural sweetener. Carob pods were historically used in various cultures as a food source and were even consumed by ancient Egyptians. Additionally, the seeds inside the pods, which have a remarkably uniform weight, were employed as a consistent measure of weight in historical trade practices. In contemporary times, the carob tree continues to be valued for its versatile applications. 

Expressions of Diamond Carat Weight


Diamond carat weight was legally established with the introduction of the Weights and Measures Act of 1963. The Metric Carat weighs 200 milligrams, 0.20 grams, or 1/5 metric gram. Alternative expressions include:

  1. Decimal Weight: Conventionally expressed to two decimal places, a half-carat diamond is denoted as 0.50cts.

  2. Fractional Carat Weight: Expressed in fractions, with 1/4 carat representing 0.25cts or a quarter of a carat.

  3. Points: Used for weights below a full carat, one carat divided into 100 points. For instance, half a carat is expressed as 50 points.

  4. Grains: A measure of weight, especially associated with pears. A grain represents a quarter of a carat or 0.25cts, with diamonds near these weights termed grainers.

  5. Melee: Refers to small groups of diamond sizes.

  6. Number of Diamonds per Carat: Expresses the approximate diamond size based on the number of diamonds that make up a carat in a specific size bracket. For example, 6pc (six per carat) diamonds are individually 0.16cts in weight.

Diamond Carat Weight Compared to Gemstones


The specific gravity of a diamond varies compared to other gemstones. As a result, the weight of a similarly sized and proportioned gemstone can be calulated. Find out how to do this in our detailed blog post on Diamond, Sapphire and gemstone weights compared.