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Gemstone & Crystal Guides

How to Read a Gemstone Lab Certificate (and Spot Fakes)

द्वारा G for Gemstones 22 Oct 2026
Sample gemstone lab certificate with a yellow sapphire and an emerald
Sample gemstone lab certificate with a yellow sapphire and an emerald

Buying guide

A gemstone lab certificate (or report) records the tests a gem lab ran on your stone and what it concluded.

It is the single most useful document when buying an astrological gemstone.

WeightIn carats
TestsRI and SG
IdentificationNatural / synthetic
CommentsTreatments noted
01

What a certificate usually shows

  • Photo of the stone
  • Weight in carats, which should match the listing
  • Measurements in millimetres and shape/cut
  • Colour description
  • Test results such as refractive index (RI) and specific gravity (SG), which help identify the mineral
  • Identification, for example “Natural Blue Sapphire” or “Natural Corundum”
  • Comments, which may mention treatments such as heating, oiling or filling
Sample gemstone lab certificate supplied by G for Gemstones
Sample of the lab certificate that comes with our gemstones
02

Natural, synthetic and imitation

  • Natural: formed in the earth
  • Synthetic (lab-grown): same mineral, made in a lab
  • Imitation: a different material, such as glass, made to look similar

For astrology, natural stones are traditionally preferred. At G for Gemstones, Thailand-origin stones are labelled by origin rather than described as natural.

03

Simple checks before you buy

  • Match the carat weight and photo on the certificate to the listing
  • Be wary of prices far below the market for the same weight and origin
  • Natural stones usually show small inclusions; perfectly clean, cheap stones deserve questions
  • Ask for a video of the exact stone
04

Does every stone need a certificate?

For primary Navratna stones, yes. For low-cost crystals and bracelets, a purity or authenticity card is common.

05

Frequently asked questions

Is ratti shown on the certificate?

No, certificates use carats. See our carat to ratti guide.

Can I see a sample certificate?

Yes, there is a sample above. For the certificate of a specific stone, WhatsApp us at +91 91080 64594.

Not sure which stone is right for you?

Message our gemstone experts on WhatsApp for photos, videos and guidance before you buy.

Browse all gemstone and crystal guides →

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