Home Knowledges How to Test Ruby Gemstones at Home: A Full Guide

How to Test Ruby Gemstones at Home: A Full Guide

by Madonna

Ruby gemstones are renowned for their vibrant red color and exquisite beauty. They have been prized for centuries and are considered one of the most valuable and sought-after gemstones in the world. Whether you’re a gem enthusiast or a jeweler, it’s essential to know how to test the authenticity and quality of a ruby gemstone. While professional gemological laboratories offer the most accurate assessments, you can perform basic tests at home to get a preliminary idea of a ruby’s quality. In this article, we will guide you through the process of testing ruby gemstones at home, ensuring you have the tools and knowledge to make an informed assessment.

The Importance of Testing Ruby Gemstones

Before delving into the specific testing methods, it’s crucial to understand why testing ruby gemstones is so important. Rubies are among the most valuable gemstones, and their value is influenced by factors like color, clarity, cut, and carat weight. By testing a ruby gemstone, you can determine its authenticity and assess its quality, which in turn affects its monetary value.


The market for gemstones is vast, and there are both natural and synthetic rubies available. Natural rubies are rare and highly prized, while synthetic or imitation rubies are more common and less valuable. Distinguishing between these two types is essential for making an informed purchase or assessment.


See Also: The Ruby Gemstone: A Comprehensive Exploration


Tools for Testing Ruby Gemstones

Before you begin testing a ruby gemstone at home, gather the necessary tools. You may not need all of these tools for every test, but having a well-rounded collection ensures you can perform various assessments with confidence. The essential tools include:

1. Jeweler’s Loupe: A jeweler’s loupe is a magnifying glass used to closely inspect gemstones. It is crucial for assessing the ruby’s inclusions, clarity, and any visible imperfections.

2. Gemological Light Source: A gemological light source, such as a gem flashlight, is used to observe the ruby’s color and transparency. It helps in identifying any fluorescence or asterism (star-like reflections) in the gem.

3. Refractometer: A refractometer measures the gem’s refractive index, which can help distinguish between different gemstones. Rubies typically have a refractive index of around 1.76.

4. Spectroscope: A spectroscope allows you to view the spectrum of light that a gemstone absorbs, providing insight into its chemical composition and potential treatments.

5. Chelsea Filter: A Chelsea filter is used to detect the presence of chromium in rubies, which is responsible for their red color. Genuine rubies should display a strong red reaction when viewed through the filter.

6. Specific Gravity Testing Kit: This kit helps determine the specific gravity of the gemstone, which can provide clues about its identity and authenticity.

7. Hardness Testing Tools: While not specific to rubies, a hardness testing kit or Mohs scale can help assess a gem’s durability and hardness. Ruby is one of the hardest gemstones, scoring a 9 on the Mohs scale.

8. Scale and Calipers: These tools are used to measure the gem’s size and carat weight, which is essential for assessing its value.

Preliminary Visual Inspection

Before using any specialized testing equipment, conduct a preliminary visual inspection of the ruby gemstone. Examine it under good lighting conditions and use a jeweler’s loupe for a closer look. Pay attention to the following characteristics:

1. Color: A genuine ruby should exhibit a vivid red color, often described as “pigeon’s blood” red. Be cautious if the color appears too pink or purplish, as this could indicate an imitation or lower-quality gem.

2. Clarity: Inspect the ruby for any visible inclusions, cracks, or imperfections. While some inclusions are common in natural rubies, a complete lack of inclusions may raise suspicions.

3. Cut: Observe the ruby’s cut and facets. A well-cut ruby will have good symmetry and light reflection. Poor craftsmanship may suggest a synthetic or low-quality gem.

4. Carat Weight: If possible, measure the gem’s size and carat weight using scales and calipers.

See Also: Where Are Rubies Mostly Found: The Origins of Precious Gems

Assessing Color and Transparency

The color and transparency of a ruby are crucial factors in its value assessment. To evaluate these characteristics, follow these steps:

1. Use Gemological Light: Examine the ruby under a gemological light source. A genuine ruby should display a rich red color with excellent transparency. Be cautious if you notice any color zoning or cloudy areas, which can indicate a lower-quality gem.

2. Check for Fluorescence: Some rubies may exhibit fluorescence when exposed to ultraviolet light. Natural rubies often fluoresce, while synthetic ones may not. This can be a helpful clue in distinguishing between the two.

3. Inspect for Asterism: Some rubies display a star-like pattern known as asterism when viewed under certain lighting conditions. This effect is due to the presence of fine needle-like inclusions, known as rutile silk, within the gem. Star rubies are highly valued for their rarity.

Determining Refractive Index

The refractive index is a critical characteristic for identifying ruby gemstones. Follow these steps to measure the gem’s refractive index using a refractometer:

1. Calibrate the Refractometer: Start by calibrating the refractometer according to the manufacturer’s instructions. This ensures accurate readings.

2. Apply a Drop of Refractive Index Liquid: Place a small drop of refractive index liquid on the flat surface of the refractometer.

3. Place the Ruby on the Liquid: Gently place the ruby on the liquid, ensuring that there is good contact. Look through the eyepiece, and you’ll see the reading on the refractometer scale.

A ruby’s refractive index typically falls within the range of 1.760 to 1.768. If the reading significantly deviates from this range, it may suggest that the gem is not a genuine ruby.

Identifying Chromium with a Chelsea Filter

The presence of chromium is responsible for the red color in rubies. A Chelsea filter is a useful tool for confirming the presence of chromium in a ruby. Follow these steps to use a Chelsea filter:

1. Prepare Lighting: Ensure you have good lighting conditions for the test.

2. Examine the Ruby: Hold the Chelsea filter up to your eye and look through it at the ruby. A genuine ruby should appear red, while other gemstones may appear green or brown.

If the gem exhibits a strong red reaction through the Chelsea filter, it’s a positive sign that you have a genuine ruby. However, this test alone cannot guarantee authenticity, as some synthetic rubies can also pass this test.

Spectroscopy for Chemical Analysis

A spectroscopy test can provide valuable insights into the chemical composition of the ruby. By analyzing the absorption spectrum, you can determine if the gemstone contains any additional elements or has undergone treatments. Follow these steps for spectroscopy testing:

1. Prepare the Spectroscope: Set up the spectroscope according to the manufacturer’s instructions.

2. Illumination: Illuminate the ruby with a light source, ensuring that the light passes through the gem and into the spectroscope.

3. Analyze the Spectrum: Look through the spectroscope and observe the absorption lines in the spectrum. Genuine rubies typically display characteristic lines indicating the presence of chromium. Some treated or synthetic rubies may show additional lines or patterns.

Spectroscopy is a highly specialized test and may require some knowledge in gemology to interpret the results effectively. If in doubt, consult a professional gemologist for assistance.

Specific Gravity Testing

The specific gravity of a gemstone is its density relative to the density of water. This test can help you identify whether a ruby is genuine or potentially another type of gemstone. Here’s how to perform a specific gravity test:

1. Weigh the Ruby: Use a scale to determine the ruby’s weight in air.

2. Weigh in Water: Submerge the ruby in a container of water, making sure it is completely immersed. Measure its weight while underwater.

3. Calculate Specific Gravity: Divide the weight in air by the loss of weight in water to calculate the specific gravity of the gem.

A genuine ruby typically has a specific gravity between 3.97 and 4.05. If the result falls significantly outside this range, it may indicate that the gem is not a ruby.

Hardness Testing

The hardness of a gemstone can be assessed using the Mohs scale. Ruby is one of the hardest gemstones, scoring a 9 on the Mohs scale. To perform a hardness test, follow these steps:

1. Select a Testing Surface: Find an inconspicuous area on the ruby where a small scratch won’t be noticeable.

2. Use a Hardness Testing Tool: Select a tool or mineral with a known hardness greater than that of the ruby (e.g., corundum or a diamond) and attempt to scratch the surface of the gem.

If the ruby remains unscathed, it indicates a high degree of hardness, consistent with a genuine ruby. Be cautious, as some imitations may also have a high hardness and could pass this test.

Consultation with a Professional

While these home-based tests can provide valuable insights into the authenticity and quality of a ruby gemstone, they are not foolproof. To obtain a definitive assessment, consider consulting a professional gemologist or sending the gem to a reputable gemological laboratory. Professionals have access to advanced testing equipment and extensive expertise, ensuring the most accurate and reliable results.


Testing ruby gemstones at home can be a fascinating and educational experience for gem enthusiasts and jewelers. While it’s essential to have the right tools and knowledge to perform these tests, it’s equally important to exercise caution and consult with professionals when in doubt. Remember that a combination of visual inspection, color and transparency assessment, refractive index measurement, and specific gravity testing can provide valuable information about the authenticity and quality of a ruby gemstone. Whether you’re considering a purchase or assessing a gem in your collection, these tests can help you make informed decisions and appreciate the exquisite beauty of this precious gem.


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