Gemstone Selling Guide

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Please Note: This is a best practice guideline created by the Gemstone selling community on bidorbuy. It is not a bidorbuy policy document.


This guide was drawn up by the Gemological Society of SA and is intended to increase consumer confidence and encourage buyers to do repeat business on bidorbuy. It serves as a way of 'levelling the playing field' between sellers so that the same standards apply to all and all have a fair chance of success.


This guide is intended for but not limited to all gemstone and jewellery articles including articles made from precious metals. The guide is an outline of the basic rules of conduct for these sales and is based on the Federal Trade Commission's (FTC): GUIDES FOR THE JEWELRY, PRECIOUS METALS, AND PEWTER INDUSTRIES. In the case of any queries with regard to the information provided herein, the FTC document shall be referred to.

  1. Misrepresentation
  2. Images
  3. Gemstone grading
  4. Weight
  5. Cut
  6. Treatments/enhancements
  7. Bulk lots
  8. Appraisals/Valuations/Value Estimates
  9. Gem Synthetics and Simulants
  10. Diamonds
  11. Additions

1. Misrepresentation

It is deceptive to misrepresent the type, kind, grade, quality, quantity, metallic content, size, weight, cut, colour, character, treatment, substance, durability, serviceability, origin, price, value, preparation, production, manufacture, distribution, or any other material aspect of an industry product. Such practice is forbidden.

2. Images

  1. It is deceptive to use any pictures or illustrations in any part of the advertisement which may, along with other visual aspects including but not limited to text or graphics, misrepresent the article being sold in any way.
  2. It is preferable to use an image of the actual product being sold.
  3. Should the images be stock images, this must be mentioned clearly and concisely in the advertisement and displayed prominently to ensure that it is visible to potential buyers.
  4. Should there be any possibility of variance in any aspects of the product as portrayed by the image, these must be clearly identified.
  5. When stock images are used, it is assumed that the image comes from the actual items in stock. Sellers cannot use images of alternative stones from other sources as this is considered an attempt to mislead. Stock photos must portray and accurate representation of the gemstone on offer.
  6. Enhancement of images through editing or digital editing is permitted only to portray the article for sale so that it is a more accurate or true representation of the product.
  7. It is deceptive to use any form of editing or digital editing to enhance to image so that it portrays the product in any other condition or size than from the actual product.
  8. Under no circumstances should images of similar goods from other sources be used as a representation of your product.
  9. It should be clearly stated that magnification of products in images is to assist the buyer in examining the product through but should not be used as a size reference.
  10. Images should be large enough to allow buyers to examine the magnified image in detail.

3. Gemstone grading

  1. Colour:

    1.1 It is deceptive to describe the colour of the stone in any way that misrepresents the colour of the actual stone. (Colour charts will be provided to give the exact hue, tone and saturation of the gemstone, details of which can accompany the seller?s description).

    1.2 Diamond colours should be given according to the internationally accepted GIA colour grading scale. Colour grading should only be attempted by trained individuals using a master colour grading set.

  2. Clarity:

    3.2.1 It is deceptive to state false grading values for gemstones - including precious and so-called semi-precious stones whether mounted or loose.

    3.2.2 Gemological Institute of America (GIA) clarity gradings are permissible, but are intended for use after examination of the gemstone by a properly trained individual under magnification of not less than 10X.

    3.3 Standard gradings with no type distinction (Non-GIA accepted international grading) are as follows:

    • Flawless VVS1 VVS2 VS1 VS2 SI1 SI2 I1 I2 I3
      Flawless/Internally Flawless = No inclusions visible, by an expert at 10X magnification.
      VVS1-VVS2 = Very, very slight inclusions very difficult for an expert to find under 10X.
      VS1-VS2 = Very slight inclusions difficult for an expert to find under 10X.
      SI1-SI2 = Noticeable, relatively easy to find under 10X. Not visible without magnification in a face-up direction.
      I1-I3 = Obvious under 10X, may be visible to the unaided eye, I3?s inclusions may affect the stone?s durability.
    • When using the above grading system in advertisements, the above table should also appear in the advertisement so that buyers can have a clear indication of the gradings portrayed.
    • As illustrated by the above system, all clarity grades above I1 are considered "eye clean" from the face-up direction.
    • GIA Grading system


      Type I
      Usually eye clean
      Aquamarine, Chrysoberyl (Yellow and Green), Heliodore, Morganite, Quartz (Smoky), Spodumene, all Tanzanite, Tourmaline (Green), Zircon (Blue).

      Type II
      Usually included
      Andalusite, Alexandrite, Corundum, all Garnet, Iolite, Peridot, Quartz (Amethyst, Citrine, Ametrine), Spinel, Tourmaline (all but Green, Red and Watermelon), Zircon (all but Blue).

      Type III
      Almost always included
      Emerald, Red Beryl, Tourmaline: Red (Rubelite) and Watermelon.


      Type I
      VVS Minute inclusions, difficult to see under 10X. Eye clean.
      VS Minor inclusions, somewhat easy to see with 10X. Usually eye clean.
      SI1 Easily noticeable with 10X. Slightly visible to the unaided eye. Usually low relief.
      SI2 Easily visible to the unaided eye. Usually low relief.
      I1 Moderate effect on appearance or durability.
      I2 Severe effect on appearance or durability.
      I3 Severe effect on both appearance and durability.

      Type II
      VVS Minor inclusions, somewhat easy to see with 10X. Usually eye clean.
      VS Noticeable inclusions under 10X. May be eye visible.
      SI1 Obvious inclusions, large or numerous under 10X. Apparent to unaided eye.
      SI2 Obvious inclusions, large or numerous under 10X. Very apparent to unaided eye.
      I1 Moderate effect on appearance or durability.
      I2 Severe effect on appearance or durability.
      I3 Severe effect on both appearance and durability.

      Type III
      VVS Noticeable inclusions under 10X. Usually eye clean.
      VS Obvious inclusions with 10X. May be eye visible.
      SI1 Prominent to unaided eye.
      SI2 Very prominent to unaided eye.
      I1 Moderate effect on appearance or durability.
      I2 Severe effect on appearance or durability.
      I3 Severe effect on both appearance and durability.
      Dcl Not transparent (Type I, Type II and Type 3)
    • If sellers do not have the necessary tools or training to facilitate the above grading, it is admissible for them to use the following gradings using the eye, unaided by any form of magnification.

      Eye-clean: For stones that display no inclusions when viewed in a face-up direction without magnification.
      Moderately included: For stones that display small, or slightly visible inclusions when viewed in a face-up direction, without magnification.
      Heavily included: For stones that display heavy and obvious inclusions when viewed in a face-up direction without magnification. This can range up to slightly translucent stones.

    • Sellers must state which grading system they are using.
    • Opaque gems cannot be graded according to clarity (unless they are so flawed and contain so many inclusions that they are rendered opaque in which case the inclusions and flaws should be fully disclosed as they could possibly be detrimental to the durability of the stone and its suitability for jewellery applications) and should therefore be listed simply as opaque.

4. Weight

4.1 Gemstones (with the exception of pearls which are measured pearl grains - p grain) are measured in carats.

4.2 A Carat (not karat - this is a measure for gold purity) is a unit of weight and not one of size. 5 carats = 1 gram.

4.3 The weight of gemstone is measured in carats.

4.4 A carat can be divided into 100 parts, called points. E.g. 1.00 carat = 100 points.

4.5 The correct and accurate weight of gemstones must always be displayed clearly in all advertisements. Gemstone weights should be accurate to at least 0.05 of a carat.

4.6 For job lots where there is a possible variance in size between units, this variance must be specified and strictly adhered to.

4.7 Pearl weight is measured in grains and not carats

1 carat (ct) = 0.2 g = 4 p grains = 0.053 m

1 gram (g) = 5 cts = 20 p grains = 0.266 m

1 pearl grain (p grain) = 0.05 g = 0.25 ct = 0.013

5. Cut

5.1 The cut of the gemstones must be accurately described.

5.2 Tables will be attached explaining various common cutting styles including so-called native or step-cutting.

5.3 Important aspects to be conveyed to buyers are the overall symmetry of the cut as well the presence of any "windowing", "bow-tie", "read through" or "fish-eye" effect and the quality of facet meets.

5.4 It should also be made clear whether or not the pavilion and crown are cut deep or shallow.

5.5 The quality of the facet surface or "polish" should be indicated.

5.6 Any chips and/or scratches must be clearly and prominently indicated.

6. Treatments/enhancements

6.1 Any treatment or enhancement procedure a gemstone has undergone must be clearly indicated. In cases where it is unknown whether or not the gem has been treated the seller should state: Treatment/enhancements: Unknown.

6.2 In the case of corundum (Ruby and Sapphire) unless information has been furnished to the contrary gems treatments should include the phrase: Heated.

6.3 With emeralds, unless information has been furnished to the contrary gems treatments should include the phrase: Oiled.

6.4 Any other treatments known by the supplier must always be disclosed and clearly displayed. Known treatments must be specified. Treatments must not simply be described as: treated.

7. Bulk lots

7.1 It should be stated clearly in both the body and title of a sale how many items are to be included in the sale.

7.2 Where the total carat weight is given for the combined items when they are to be sold individually, an indication of carat weight and size must be given for the individual items.

7.3 If there are ten items or less, individual information should be supplied on each gem stone.

7.4 Should the bulk items have any variance of any sort between gemstones, this must be stated clearly and prominently.

8. Appraisals/Valuations/Value Estimates

8.1 Written valuations/appraisals should be performed by independent third party jewellers or Gemmologists. Jewellers should not be used to value gemstones unless already set in a jewellery piece and then only on the value of the piece as a whole based on what they believe the stone to be.

8.2 It should be noted that most jewellers are goldsmiths or jewellery designers and do not have the necessary training to accurately identify gemstones. In such a case the appraisal is on the item as a piece and not on the gemstone.

8.3 The appraiser should be clearly identified in the listing and details of certificates to be provided given.

8.4 Where the seller is properly qualified to issue gemstone identification reports/certificates it is permissible, however appraisals/valuations will be frowned upon (and if reported, compared against comparative goods, to establish whether or not the price is legitimate) unless issued by an independent third party. It is unacceptable for sellers to make up their own value estimates or attempt to guess at or inflate any estimates at any time. Any attempt at such will be viewed as gross misrepresentation.

8.5 Value estimates should be undertaken using the standard provided estimated value chart or from the web based value estimate provided by Gemval. The valuation estimates must be marked clearly as such in the advertisement with any criteria entered in to come to the results.

8.6 The standard provided estimated value chart will contain estimated values only and will be available for buyers to examine for more information on the listing. It will also include ratios of certain gems to establish their value after having undergone certain treatments (e.g. Be treatment of sapphires).

8.7 It must also be stated that the estimated values are for reference only and are based only on the data which was entered, any of which could have an impact on the price if incorrect.

8.8 Any valuations/appraisals should indicate whether they are market (trade), wholesale or retail value.

8.9 No other external price-estimating service will be accepted unless first submitted for approval after which it will be added to this document.

9. Gem Synthetics and Simulants

9.1 Synthetic, refers to gems (including pearls) that have been synthesized and have the optical, physical, and chemical properties of their natural counterpart.

9.2 "Synthetic", "cultured" (in the case of pearls), "laboratory-created", laboratory-grown" and "man-made" are terms which can be used to describe synthetic gems. These words must appear in the main title of the advertisement.

9.3 Simulants are imitations of the actual gem and do not share the chemical make-up or properties of their natural counterpart. The word "simulated" or "imitation" must appear in the main title of the advertisement.

9.4 It is misrepresentation and fraudulent to attempt to sell either synthetic or simulated stones as their natural counterparts or to fail to disclose that they are not natural. It is also a misrepresentation to claim attributes to any synthetic or simulated stones which the actual article does not possess.

9.5 In the case of diamond simulants it is permissible to use the terms "diamond-like", "imitation diamond" or "simulated diamond". This must also appear in the main title of the advertisement.

9.6 The following phrases are misleading and are therefore not permissible: "Diamond CZ", "Diamond Moissanite", or any other phrases which imply that there is an actual diamond being advertised.

9.7 With all simulants the phrase, "this/these is/are an imitation of their natural counterpart/s and should not be confused with the genuine article" should be displayed prominently in the advertisement.

9.8 With all synthetics the phrase "this/these is/are man-made versions of their counterpart/s found in nature and while they share the optical, physical, and chemical should not be confused with the natural article" should be displayed prominently in the advertisement.

9.9 It is deceptive to use the word "real", "genuine", "natural", "precious", "semi-precious" or similar terms to describe any industry product that is manufactured or produced artificially.

9.10 Use of the word "gem" with respect to synthetic stones should be avoided as few possess the necessary attributes to properly be termed "gems".

9.11 Simulants should never be described as "gems".

9.12 Not all diamonds or natural stones, including those classified as precious stones, possess the necessary attributes to be properly termed "gems".

10. Diamonds

10.1 All above gemstones rules apply so diamonds with the following additions:

10.2 Diamonds are to be graded using the internationally accepted GIA colour grading system.

10.3 The colour of a diamond refers to the amount of yellow, brown or gray body colour that a stone possesses. The G.I.A. scale starts at "D" and goes through "Z". "D" being colourless, and "Z", having a light yellow brown or gray colour.

10.4 Diamond colour gradings should be performed by properly qualified persons only using a master diamond colour grading set.

10.5 Any other colours are known as "fancy colours" and require specialised grading.

10.6 As above, all treatments and enhancements (including but not limited to all treatments mentioned above as well as HPHT treatment, laser drilling and glass filling) must be disclosed as these can dramatically affect the value of the diamonds.

10.7 No simulated diamond (Glass, CZ, Moissanite, Paste etc) advertisements should use the word "diamond" in their main title and at no point should they be referred to as such. Where weight is given as the equivalent diamond weight, the actual weight of the simulant must also be supplied.

10.8 The cut used in diamonds should be correctly described as this can directly impact on the brilliance and dispersion qualities of the stone. The preferred cut for diamonds is a round brilliant.

10.9 For stones over 0.5 carats in weight, proportions (or measurements) should be given for the table, girdle, pavilion and culet. When possible, it is preferable to also state the table and pavilion angles. These all affect the value of the diamond.

11. Additions

This guide will have additions added as the information becomes available or international standards alter because of new findings or for any other reason. Any additional submissions will be posted on the forum for full display to all parties and opportunity given for comment thereon after which they will be added to the rules on the agreement on the majority.