Gemstones Premium Positioning
Authenticity - Quality
At Catawiki we auction the best gemstones of premium quality which are hard to find and appealing to passionate gemstone enthusiasts.
Because potential buyers come to Catawiki looking for special and rare gemstones, our in-house experts select every piece for our auctions, ensuring they are of premium quality and are presented in the best possible way.
We do this because we aim to keep our bidders excited, allowing them to find the pieces they’re interested in and ensure our sellers have great selling experiences.
At Catawiki we auction gemstones gathered from all corners of the world.
For our auctions we seek and select:
- a wide range of natural gemstones and gemstones with selected standard treatments (or without treatments)
- gemstones that are in a decent condition and that have a sufficient quality in cut and clarity to be mounted in jewellery
- gemstones that are accompanied by a trusted gemmological certificate
- gemstones that have a minimum estimated lot value of €100 (as single stones, or, for selected gemstones offered as parcel)
Certified natural gemstones of premium quality
For our gemstone auctions, we seek a wide range of natural gemstones that are accompanied by a trusted gemmological certificate (see details further on). This includes:
- Beryl, all types (emerald, aquamarine, morganite etc.)
- Corundum (all colours of sapphire, ruby)
- Tanzanite (and zoisite)
- Spinel (all colours)
- Chrysoberyl (incl. cat’s eye and alexandrite)
- Opal (all crystal types, fire opals etc.)
- Garnet (all colours)
- Tourmaline (all colours)
- Zircon (all colours)
- Topaz (all colours)
- Star corundum
- Quartz (amethyst, ametrine, citrine)
- Pearl, jade and other selected rare species, e.g. benitoite or taaffeite
✘ Amber, coral as well as lab grown gemstones (synthetic) and composite gemstones are not suitable.
Selection of uncertified natural gemstones
Certain gemstones may be offered in a multiple stone lot, without a gemmological certificate. This only applies to gemstones that have an individual value below €100 and that comply with all other quality requirements. This also includes:
- Microcrystalline quartz (such as carnelian, jasper, tiger eye or petrified wood)
- Lapis lazuli
- Rose quartz/rock crystal/smoky quartz
- Smoky quartz, rock crystal
Faceted and cut gemstones
For our dedicated Gemstone auction, we select faceted and cut minerals (gemstones), as well as polished minerals, e.g. cabochons, that are small and ready to be mounted in jewellery.
This includes cuts such as:
- brilliant, oval, emerald, pear, cabochon, marquise, cushion, trillion, square, princess, baguette, radiant, heart, fancy
Any cut needs to be of decent quality, good enough to be used in jewellery. This is determined by e.g.:
1) Proportions (symmetry, crown height etc.)
2) Light performance (brilliance, windowing etc.)
3) Finish (polish)
✘ Gemstones that show low quality in all above criteria may be found unsuitable for our auctions.
Rough gemstones, slices, large carvings, spheres, balls, or eggs are more suitable for our Minerals auction.
Clarity & condition
For our auctions, we accept gemstones that are undamaged and have a decent clarity. This means that the item submitted:
- may be transparent, translucent or opaque, depending on the gemstone - for some gemstones, the value strongly decreases if they are not transparent (such as tanzanite or aquamarine)
- may present inclusions (for example emerald could present inclusions)
- may have single small chips on girdle/facets or some signs of wear - these gemstones may be accepted (without a reserve price) as long as they are clearly disclosed in pictures and in the description
✘ If the gemstone contains inclusions that affect the visual beauty of the gemstones (because the light cannot be reflected well or the colour is masqued by the inclusions), the expert can decide not to approve it.
Accepted standard treatments
The following standard treatments are accepted for selected gemstones:
- Heat treatment for corundum, tanzanites, citrine, amethyst, ametrine, zircon, tourmaline and pink topaz
- Oiling for emeralds
- Irradiation for blue topaz
- For jade: waxing (A-jade) or bleaching and impregnating with a polymer resin (B-jade)
The following treatments are not suitable for our auctions:
- Materials such as emeralds, sapphires, spinels etc. that have had non-traditional coloured material such as dyes, coloured oils and coloured fillers (such as lead glass)
- Coating, as it might give a false appearance to the gemstone, (e.g. Mystic Topaz etc.)
|composites (such as doublets, triplets)||beryllium (lattice) diffused (sapphires)|
Authenticity / Certification Requirements
Buyers are more likely to bid on your lot if they know it’s certified as being authentic. This is why we ask to see certificates from trusted gemmological institutes for certain high valued types of gemstones.
- All gemstones generally valued at €75-€100 or more require a certificate from our list of approved gemmological laboratories, as listed on the next slide.
- Sellers who have a degree in Gemmology may offer in the ‘Certified Gemmologist Auctions’ without a certificate (after being approved by our experts) but, for gemstones valued above €950, they still need to add a gemmological report.
- Gemstones that have an individual value below €75 can be offered in homogeneous parcels (2 or more) to the Parcels of Gemstones auction, without a certificate.
List of suggested trusted gemological institutes
Certificates of these laboratories are generally considered to carry sufficient details:
|Certificates of the following laboratories may be accepted in certain cases:|
|Please be aware that we do not consider certificates of the following laboratories:|
Register as a seller to begin selling your gemstones on Catawiki, then start submitting your objects for auction right away.