Diamonds Guidelines

Acceptance & Submission Guidelines Diamonds

Diamonds Premium Positioning

Because potential buyers come to ONEGEM looking for special and rare diamonds, our in-house experts select every piece for our marketplace, ensuring they are of premium quality and are presented in the best possible way.
We do this because we aim to keep our buyers excited, allowing them to find the pieces they’re 
interested in and ensuring our sellers have great selling experiences.
At ONEGEM, we trade diamonds of premium quality which are hard to find and appealing to passionate diamond enthusiasts and collectors. 

At ONEGEM , we are constantly moving forward. Our positioning is evolving into a strong premium segment which opens up opportunities for success for us and for you.
From the million visitors that come to our platform every month, we gain valuable information on what they are passionate about and what they prefer to buy.
With your help, we want to make sure we continuously meet this demand and offer the special objects that our growing number of bidders are excited about and want to buy.
In these guidelines, we’ve defined what the special pieces are that buyers look for in our diamond 
marketplace. We’ll also state what we require from you to successfully place them in auction. These guidelines serve to create a level playing field between all our sellers.
We will be happy to make room in our marketplace for your products that meet this high quality demand, and we will aim to shape ourselves to better fit you.
Our experts and account managers will fully support and guide you for success on ONEGEM.
Thank you for being with us on this exciting journey!

Product Guidelines
For our marketplace we seek and select:
● cut diamonds as well as rough diamonds that are of quality, in all colour ranges except opaque 
● in the case of rough diamonds, diamonds that are always accompanied by a gemmological certificate, of valuable appearance and suitable for jewellery mounting 
● diamonds of all clarities, except diamonds with inclusions causing opaqueness (for other exceptions see the Clarity Table), of decent condition and that have a sufficient 
quality in cut and clarity to be mounted in jewellery 
● diamonds that are accompanied by a trusted gemmological certificate
● products that have a minimum estimated value of €500
At ONEGEM we trade diamonds gathered from all corners of the world

CERTIFIED NATURAL DIAMONDS OF PREMIUM QUALITY
For our diamond marketplace, we seek a wide range of natural diamonds that are accompanied by a trusted gemmological certificate (see details further on). This includes:
1) White natural diamonds (D-J color)
2) Light and very light natural diamonds (K-Z color)
3) Natural fancy colour (NFC) diamonds

WE DO NOT ATTECPT
1) Colour treated diamonds
2) Clarity Enhanced diamonds
3) Lab grown diamonds

DIAMOND CUTS
For our dedicated diamond marketplace, we select cut diamonds that are ready to be mounted in 
jewellery:
This includes cuts such as:
1) Brilliant cut
2) Fancy cut
3) Laser cut
4) Old cut

Cuts that are NOT suitable are:
1) 8/8 single cut 
2) Swiss cut
3) Damaged and broken cuts

COLOUR CONDITIONS

Colour grade accepted
1) White D to Z 
2) Natural fancy

Colour grade NOT accepted
1) Colour treated (CT) irradiated/HPHT
2) CT black(ish) (opaque)
3) Colour coated

Clarity conditions
we accept diamonds that are of suitable clarity or in more specific terms, belong in a 
certain clarity range. This means that the items suitable for this auction are as follows:

Clarity grade accepted
FL to I3
Clarity I1, I2 & I3 have a minimum total carat weight requirement 

Clarity grade NOT accepted
Fracture filled (CE) clarity grade IF to SI1
Laser drilled clarity grade IF to SI1
Heavy inclusions causing opaqueness

NOT ACCEPTED TREATMENTS

The following standard treatments are NOT accepted for our selected diamonds:
1) Irradiation treatment, which leads to a variety of coloured 
diamonds (for example: yellow, orange, pink) 
2) HPHT (high-pressure, high-temperature) treatment
3) Fracture filled (CE) with clarity grade ranging from FL to SI1
4) Laser drilled with clarity grade ranging from FL to SI1
5) Colour coated 

CONDITION
For our marketplace, we accept diamonds that are natural, undamaged and have a decent clarity. 
This means that the items submitted:

May present small damage, but the seller needs to declare these damages and there should be a possibility of repair through recutting or repolishing.

Submissions with damages that would lead to them breaking during the setting procedure are not suitable for our marketplace.

The expert reserves the right to reject a submission if the scratches/damages surpass a 
level and the value of the diamond is affected.

Authenticity / Certification Requirements

Buyers are more likely to buy your gemstone if they know it’s certified as being authentic. 
This is why we always ask to see certificates from trusted gemmological institutes for all our submissions.

Examples of trusted authentication certificates

These following certificates are generally considered to carry sufficient details to be trusted by our experts:

● GIA - Gemmological Institute of America (worldwide)
● HRD - Hoge Raad voor Diamant (Antwerp)
● IGI - International Gemological Institute (worldwide)
● AIG - International Gemological Laboratories (Antwerp)
● IGE - Instituto Gemologico Espaniol (Spain)
● NEL - Nederlands Edelsteen Laboratorium (Netherlands)
● IGI - Istituto Gemmologico Italiano (Italy) 
● CISGEM - Centro informazioni e servizi gemmologici (Italy) 
● SSEF - Swiss Gemmological Institute (Switzerland)
● GRS - GemResearch Swisslab AG (Switzerland)

Submission Guidelines
Potential buyers are more likely to buy gemstones with a good description, all relevant 
information displayed clearly and, of course, beautiful photos.

Gemstone Description
To help encourage potential buyers to buy your gemstone, you should include a detailed 
description of your object(s). This should be thorough and honest, and follow this 
guidelines:

If you are using our website to upload your gemstones, tips will appear to give you guidance about what information we need to know about your gem. The fields that you fill in help to present the information in a way that’s easy for the buyer to read. 
The required information includes:

● Diamond weight (in carat)
● Cut 
● Colour (please mention treatment if applicable) 
● Clarity (please mention treatment if applicable) 
● Treatment
● Certificate (number certificate, date and place)
● Sealed in blister if applicable - laser inscribed if applicable 
● Additional description: all detailed and relevant information about the diamond, shipping, tax etc.

When adding extra details, please mention any additional cost or additional steps that the buyer 
might come across when purchasing your item.

Including strong photographs is key to catching buyers’ eyes, ensuring they buy 
your gemstone.
Of course, buying online means potential buyers do not get a chance to see your gemstone 
in person, therefore detailed and high quality photographs are very important.

Photographs
To allow our experts, as well as our bidders, to get the right impression of an item, we require: 
● a 360 degree view of the item
● clearly readable image(s) of the 
certification report

Photograph the diamond in front of a plain and neutral background, preferably a white wall.
● Photos should show nothing else but the diamond(s) you want to put up for auction and the paper 
certificate in its own picture.
● Make sure you avoid any distracting background, only the loose diamond, the sealed or the paper 
certificate are allowed in the picture.
● All images must be original photographs taken by the seller. Stock pictures, other sellers’ pictures and screenshots are not suitable. Images in which the object is held by a person are not 
appropriate.
● Buyers are interested in seeing as many details as possible. Therefore, please always include 
images of the top and back of the blister in sealed diamonds and the crown, girdle and pavilion in 
loose diamonds. If you have several items in one lot, please photograph all offered items together 
as well as every item separately. All submissions require a photograph of the paper certificate.
● Provide sharp, specific images of details, such as inclusions. Unenhanced images are preferred. 

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