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Unlocking the Mysteries of Gemstones: How the FABLE Refractometer Ensures Accurate Identification

In the world of gemology, accurate identification and differentiation of gemstones are crucial. The refractive index (RI) of gemstones is one of the most stable and reliable data points, as each gemstone has a unique RI. Detecting this RI with a high-quality gem refractometer, such as those produced by FABLE, can effectively reveal the gemstone’s identity.

Examples of Refractive Indices for Common Gemstones

Gemstone Name Refractive Index Reference Value
Emerald 1.577-1.583
Ruby 1.762-1.770
Chrysoberyl Cat Eye 1.746-1.755
Tanzanite 1.691-1.700

Scenarios for Using a FABLE Gemstone Refractometer

  1. Identify Unknown Gemstones When you come across a beautiful gemstone, a FABLE gemstone refractometer can help you determine its type by measuring its refractive index. For instance, if a blue gemstone’s RI is found to be between 1.762 and 1.770, it can be identified as a sapphire.
  2. Distinguish Similar Gemstones A batch of red gemstones, including ruby, red glass, red spinel, red tourmaline, red scapolite, and red garnet, may look visually similar. A FABLE refractometer can measure their RIs to differentiate them. Here are some RIs for common red gemstones:
    • Ruby: 1.762-1.770
    • Red Tourmaline: 1.624-1.644
    • Red Spinel: 1.718
    • Red Scapolite: 1.550-1.564
    • Red Garnet: 1.714-1.743
    • Red Glass: 1.4-1.7
  3. Purchase Gemstones Bringing a FABLE refractometer to the market can help you avoid fakes. This portable device allows for on-the-spot testing, ensuring you purchase genuine gemstones.
  4. Help Friends Identify Gems If your friends have unidentified gemstones, you can assist them by using a FABLE refractometer. This service can enhance friendships, provide valuable experience, and even earn you a fee.
  5. Outdoor Treasure Hunting During gem digging adventures, once you find gemstones, you can polish them and use a FABLE refractometer to measure their RIs and determine their type.
  6. Academic Research and Education In educational settings, FABLE refractometers are used in geology and gemology courses. Students and researchers can study various gemstones, understanding their properties and characteristics.
  7. Jewelry Appraisal Professional appraisers use FABLE refractometers to authenticate and value gemstones in jewelry, providing precise valuations and ensuring fair transactions.
  8. Quality Control in Gemstone Cutting In gemstone cutting workshops, FABLE refractometers verify the type of gemstones being processed, ensuring correct procedures and preserving the gemstones’ quality.
  9. Gemstone Collection and Curation Collectors and curators use FABLE refractometers to catalog and verify their collections, ensuring each gemstone is correctly identified and documented.
  10. Trade Shows and Exhibitions Vendors at gem and jewelry trade shows use FABLE refractometers to demonstrate the authenticity and quality of their gemstones, facilitating sales by providing on-the-spot verification.

Characteristics of a Quality FABLE Gem Refractometer

A qualified gem refractometer must have the following characteristics to ensure precise measurements:

  1. Monochromatic Light Source, Wavelength 589.5nm:
    • All RI standard data are tested in a 589.5nm monochromatic yellow light environment. A qualified refractometer must have sufficiently pure 589.5nm yellow light.
    • The interior must be well-sealed to prevent outside light from affecting the purity of the light source.
  2. Prisms with High Hardness and High Refractive Index:
    • The gemstone needs to contact the prism during testing. High hardness ensures the prism is durable and extends the instrument’s service life.
    • The prism’s RI must be greater than that of the gemstone to ensure accurate detection.
  3. Refractive Liquid with High Light Transmittance and High Refractive Index:
    • The refractive liquid must have sufficient light transmission properties, and its RI must be greater than that of the gemstone being tested.
  4. Easy to Disassemble Polarizer:
    • A polarizer is needed for faceted gemstones but not for cabochon gemstones. The polarizer must be easy to disassemble for flexible use.
  5. Clear and Accurate Reading Scale:
    • The scale must be clear and accurate to ensure the detected RI is perfectly presented for reading.

FABLE’s gem refractometers incorporate all these essential characteristics, ensuring reliable quality and precise results.

Gem refractometer

What are the characteristics of a quality gem refractometer?

Only a qualified gem refractometer can accurately detect the refractive index of gems. A qualified gem refractometer needs to have the following characteristics:

  1. Monochromatic light source, wavelength 589.5nm;
  • All refractive index standard data of gemstones are tested in a 589.5nm monochromatic yellow light environment, so a qualified gem refractometer must have sufficiently pure 589.5nm yellow light;
  • The interior of the gem refractometer is well sealed, and outside light cannot shine into the interior of the instrument. If external light enters the interior of the gem refractometer, the input light source of the instrument will not be pure 589.5nm yellow light, and the detected refractive index data will be inaccurate.

Prisms with high hardness and high refractive index;

①.When detecting the refractive index of a gemstone, the gemstone need to be in contact with the prism,so only when the hardness of the prism is high enough can it be ensured that the prism is not easily worn out and the service life of the instrument will be longer;

②.To make sure the refractive index of the gemstone can be accurately detected,the refractive index of the prism must be greater than the gemstone to be detected.

refractive liquid with high light transmittance and high refractive index;

To make sure that the refractive index of the gemstone be accurately detected,the refractive liquid must have sufficient light transmission properties, and the refractive index of the refractive liquid must be greater than the gemstone being tested.

Easy to disassemblepolarizer;

When detecting faceted gemstones, a polarizer must be installed, meanwhile when detecting cabochon gemstones, a polarizer is not required. so the polarizer must be easy to disassemble for flexible use.

Clear and accurate reading scale.

The scale must be clear and accurate to ensure the detected refractive index be perfectly presented for reading out.


A FABLE gemstone refractometer is a versatile and indispensable tool for gemologists, jewelers, appraisers, collectors, and enthusiasts. By measuring the refractive index, it provides a reliable method for identifying and distinguishing various gemstones in different settings, from marketplaces to educational institutions. FABLE’s commitment to quality and precision makes their gem refractometers an essential instrument in the world of gemstone identification and appraisal.

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