How to Tell If a Blue Sapphire is Real – A Beginner’s Guide

How to Tell If a Blue Sapphire is Real – A Beginner’s Guide – Blue sapphire is a precious gemstone that has been treasured for centuries. Known for their striking blue color, sapphires are often used in engagement rings, necklaces, and other fine jewelry pieces.

However, not all blue sapphires are created equal. Some are genuine, while others are simply imitations or even synthetic.

So, how can you tell if a blue sapphire is real? In this beginner’s guide, we’ll go over the basic characteristics of a genuine blue sapphire and how to spot a fake one.

The Four Cs of Blue Sapphire

When it comes to evaluating the quality of blue sapphire, there are four key factors to consider. These are known as the “Four Cs” of sapphires, which include color, clarity, cut, and carat weight.


The most important factor in determining the value of blue sapphire is its color. A genuine blue sapphire should have a rich, deep blue color that is evenly distributed throughout the stone. The color should also be consistent, with no visible color zoning or patches of different shades.

One way to test the color of blue sapphire is to look at it in different lighting conditions. A genuine sapphire will have a consistent color under both natural and artificial light. If the color of the stone appears to change under different lighting conditions, it may be a fake.


Like diamonds, blue sapphires can have internal and external flaws, known as inclusions and blemishes. The clarity of a blue sapphire refers to the absence of these flaws. A genuine sapphire should be free of any visible inclusions or blemishes when viewed under 10x magnification.

However, it’s important to note that some inclusions are acceptable in blue sapphires, as they can be used to help identify the stone’s origin. For example, sapphires from Sri Lanka may have small silk-like inclusions that are unique to that region.


The cut of a blue sapphire refers to its proportions, symmetry, and polish. A well-cut sapphire will have a symmetrical shape with smooth, polished facets that reflect light evenly. The proportions of the stone should also be well-balanced, with no areas that appear too shallow or too deep.

A poorly cut sapphire may appear dull or lifeless, with uneven facets that cause light to leak out of the stone. It’s important to note that the cut of sapphire can also affect its carat weight, as a poorly cut stone may be heavier than a well-cut one.

Carat Weight

The carat weight of a blue sapphire refers to its size, with one carat equaling 0.2 grams. Like diamonds, the value of a blue sapphire can increase significantly as its carat weight increases. However, it’s important to note that a larger stone does not necessarily mean a higher quality stone. A small, high-quality sapphire can be more valuable than a larger, lower-quality one.

Other Tests for Identifying a Real Blue Sapphire

In addition to the Four Cs, there are other tests you can use to identify a real blue sapphire. Here are a few to keep in mind:

The Scratch Test

A genuine blue sapphire is one of the hardest gemstones in the world, with a rating of 9 on the Mohs scale. This means that it should be able to scratch materials that are softer than itself, such as glass or metal.

You can perform a scratch test on a blue sapphire by gently scraping it against a piece of glass or metal. If the stone leaves a scratch, it is likely genuine. However, if the stone is scratched or damaged, it may be a fake.

UV Light Test

Some blue sapphires contain trace elements that cause them to fluoresce under ultraviolet (UV) light. To perform a UV light test, shine a UV light on the sapphire and observe its reaction.

A genuine sapphire will typically exhibit a weak to moderate blue fluorescence, while a fake sapphire may not fluoresce at all.

Refractometer Test

A refractometer is a tool that measures the refractive index of a gemstone. A genuine blue sapphire should have a refractive index between 1.757 and 1.779. If the refractive index of the stone is significantly higher or lower than this range, it may be a fake.

Heat Test

Heat treatment is a common process used to enhance the color and clarity of blue sapphires. However, not all blue sapphires are heat-treated, and some may be damaged by exposure to high temperatures.

To perform a heat test, heat a small portion of the sapphire with a lighter or torch for a few seconds and then cool it rapidly with water. If the stone is damaged or cracks under the heat, it may be a fake.


In conclusion, there are several factors to consider when determining if a blue sapphire is real. These include the Four Cs of sapphires (color, clarity, cut, and carat weight), as well as other tests such as the scratch test, UV light test, refractometer test, and heat test.

By examining these characteristics and performing the appropriate tests, you can increase your chances of identifying a genuine blue sapphire.

Remember to always purchase your gemstones from reputable dealers and to ask for a certificate of authenticity to ensure that you are getting the real thing.

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