Opal
Opal is hydrated amorphous silica. In precious opal the silica spheres are stacked regularly enough to diffract light, which produces the shifting spectral flashes the trade calls play of colour, and in common opal they are not, which produces a solid body colour. It carries several percent water in its structure, which makes it softer and more sensitive to heat and dehydration than the crystalline gemstones, and it is cut as cabochons, freeforms, carvings and inlay rather than as faceted stones. It is used in fine and designer jewellery, in collector specimens, and in doublets and triplets where a thin colour bar is backed and capped.
Listed opal markets
Each line is a grade at a delivery point. Open one for its full specification and terms.
Grades
Opal is bought on the play of colour and the body tone, and on whether the piece is solid or assembled. The contract states the type, the body tone, the pattern, the assembly status and any treatment, because an assembled or treated stone is a different product at a different price.
Species, variety and identification
8 grades
| Grade | Definition |
|---|---|
| SpeciesOpal, confirmed by gemmological testing | Hydrated amorphous silica, confirmed against the constants of the species. |
| TypeDeclared, as precious opal or common opal | Precious opal shows play of colour. Common opal does not and is sold on body colour alone. |
| Refractive indexReported | Measured on a refractometer. Opal reads low against the crystalline gem species. |
| Specific gravityReported | Measured hydrostatically. Opal is light for its size, and the water content is part of why. |
| HardnessReported on the Mohs scale | Soft relative to the crystalline gemstones, which governs how it is set, worn and handled. |
| Water contentDeclared, as measured or as characteristic of the origin | Structural water. It governs the stability of the stone and the risk of crazing, and it is the single most important durability term in opal. |
| Optical characterAmorphous | Isotropic and non crystalline, which is the identification that separates opal from every faceted species. |
| Host and matrixDeclared, as solid, boulder with ironstone host, or matrix | Whether the material is a solid stone, a colour bar attached to its natural host, or colour distributed through a porous host. |
Colour
7 grades
| Grade | Definition |
|---|---|
| Body toneDeclared against the standard body tone reference set, from black through dark and grey to light, white and crystal | The background the play of colour sits on. It is the primary value dimension in opal and it is judged against a physical reference set, not scored. |
| Play of colourDescribed, by the spectral colours present and their coverage | Which colours appear, over how much of the face, and how they behave as the stone is tilted. Red is the scarcest and blue the most common. |
| PatternNamed, using the established pattern terms | Harlequin, broad flash, pinfire, rolling flash, ribbon, floral and the other named patterns. The name is a description of the arrangement, not a rank. |
| BrightnessDescribed against the standard brightness reference set | How strongly the play of colour reads at the stated viewing distance and lighting, judged against a physical reference set. |
| DirectionalityDescribed | Whether the play of colour holds through the full rotation of the stone or extinguishes in some directions. |
| Transparency and diaphaneityDescribed, from transparent through crystal and translucent to opaque | Crystal opal, jelly opal and opaque opal are separate products. |
| Lighting conditionDeclared | Assessed under daylight equivalent lighting, because opal changes markedly under different light. |
Clarity and inclusions
5 grades
| Grade | Definition |
|---|---|
| Inclusion and matrix contentDescribed, by type and position | Sand, potch, ironstone, webbing and other host material in the face of the stone. |
| CrazingDeclared, as present or not observed, with the position of any observed cracking | Fine surface cracking from dehydration or stress. It is the defining durability defect in opal and it must be declared explicitly. |
| FracturesDescribed, by position and reach | Breaks in the stone or along the colour bar. |
| Potch contentDescribed | The proportion of colourless silica in and behind the colour bar, which governs both appearance and cutting yield. |
| Stability declarationDeclared, with the length of time the material has been out of the ground | Opal is allowed to stabilise after mining before it is cut, and the declaration is a standard term of sale in rough. |
Rough form, size and yield
6 grades
| Grade | Definition |
|---|---|
| Rough weightGrams or carats, per piece and per parcel | Weighed on a calibrated balance. Rough opal is commonly traded by the gram and finished opal by the carat. |
| DimensionsMillimetres, length by width by depth | Measured on the piece, because opal is sold on face area as much as on weight. |
| Colour bar thicknessMillimetres | The depth of the layer carrying the play of colour. It decides whether the piece cuts as a solid stone or only as a doublet. |
| Estimated yieldPercentage of rough weight, declared as an assessment | An opinion of the seller or the inspecting cutter, never a warranty. |
| FormDeclared, as nobby, seam, boulder split, matrix or rubbed preform | The natural form governs how the piece is worked. |
| Size distributionDeclared, as the count within each stated weight or size band | For a sorted parcel, the distribution across sizes. |
Treatment and disclosure
7 grades
| Grade | Definition |
|---|---|
| Assembly statusDisclosed, as solid, doublet or triplet | A doublet is a colour bar on a backing. A triplet adds a clear cap. Both must be disclosed and both are priced as separate products from a solid stone. |
| Smoke and sugar treatmentDisclosed | Carbon or sugar and acid darkening of porous material to deepen the body tone. Permanent and identifiable, and disclosed in every case. |
| DyeingDisclosed, with the substance identified | Any applied colourant. |
| Impregnation and stabilisationDisclosed, with the substance identified | Resin, plastic or oil used to stabilise porous material, with the extent stated. |
| Backing and setting treatmentDisclosed | Any adhesive backing, coating or applied layer. |
| Synthetic and imitation screeningDeclared, against the named laboratory method | Confirmation that the stone is natural opal rather than laboratory grown opal, opal simulants or plastic imitation. |
| Disclosure recordDocument, per stone or per parcel | The written treatment and assembly disclosure on the invoice and with the parcel. |
Parcel, documentation and settlement
9 grades
| Grade | Definition |
|---|---|
| Parcel compositionDeclared, by piece count and total carat weight | What is actually in the lot. A rough parcel is sold as a parcel, so the count, the weight and the size distribution are the contract. |
| Weight basisCarats, to the stated decimal place | Weighed on a calibrated balance, with the weighing certificate and the tolerance named. |
| Sealing and markingDeclared | Parcels sealed in the presence of both parties or their agents, numbered and photographed, so the goods that arrive are the goods that were inspected. |
| Laboratory reportDocument, per stone or per parcel | Issued by a named laboratory operating to the international testing competence standard, covering species, treatment and, where commissioned, origin. |
| Origin determinationDeclared, where commissioned | A laboratory origin opinion is an opinion based on inclusion suites and trace element chemistry. It is stated as such and never as a guarantee. |
| Export and import documentationDeclared | Export permit or certificate from the producing country, customs classification under the harmonized system, and any royalty or clearance certificate the origin requires. |
| Responsible sourcingDeclared | Mine or source, chain of custody, and the due diligence statement, including artisanal and small scale mining status where it applies. |
| Viewing and rejectionDeclared | Where and when the buyer may view, the memo or consignment terms if any, and the window and grounds for rejection after the laboratory report. |
| Insurance and carriageDeclared | Valuation for transit, the specialist carrier or secure courier named, and the point at which risk passes. |
Grades outside this list trade on request. Send us the contract specification you work to and we will price against it.
Locations
| Country | Region | We trade it as |
|---|---|---|
| Australia | Oceania | Origin and destination |
| Ethiopia | East Africa | Origin and destination |
| Mexico | North America | Origin and destination |
| Brazil | South America | Origin and destination |
| United States | North America | Origin and destination |
| Peru | South America | Origin and destination |
| Indonesia | Southeast Asia | Origin and destination |
| Madagascar | Southern Africa | Origin and destination |
| Tanzania | East Africa | Origin and destination |
| Mozambique | Southern Africa | Origin and destination |
| Czechia | Europe | Origin and destination |
| Turkey | Western Asia | Origin and destination |
| Russian Federation | Eurasia | Origin and destination |
| Kazakhstan | Central Asia | Origin and destination |
| Hong Kong | East Asia | Trading centre |
| Singapore | Southeast Asia | Trading and finance |
| China | East Asia | Cutting centre and destination |
| Japan | East Asia | Destination |
| Republic of Korea | East Asia | Destination |
| India | South Asia | Cutting and trading centre |
| Thailand | Southeast Asia | Cutting, treatment and trading centre |
| Israel | Middle East | Cutting and trading centre |
| United Arab Emirates | Middle East | Trading hub and free zone |
| Switzerland | Europe | Trading, laboratory and vaulting centre |
| Germany | Europe | Cutting centre and destination |
| United Kingdom | Europe | Trading centre and destination |
| France | Europe | Destination |
| Italy | Europe | Destination |
| Spain | Europe | Destination |
| New Zealand | Oceania | Destination |
| Canada | North America | Origin and destination |
Origins and destinations outside this list trade on request. We are not limited to the locations shown here.
Timing
Production is when the stone comes out of the ground at origin, which follows the mining season, the water level at an alluvial working and the rhythm of artisanal digging rather than a crop calendar. Arrival is when material from that origin typically reaches a cutting or trading centre. The gap between them is sorting, export clearance and the journey to the market.
HarvestArrival
| Origin | J | F | M | A | M | J | J | A | S | O | N | D | Window |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Australia | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest Jan to Dec, arrival Jan to DecThe reference origin. Lightning Ridge black opal, Coober Pedy and Mintabie light and crystal opal, and Queensland boulder opal, produced and shipped year round. |
| Ethiopia | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Arrival | Arrival | Harvest | Harvest | Harvest and arrival | Harvest Oct to Apr, arrival Dec to JunWollo and Shewa hydrophane opal, worked around the main rains. Hydrophane material absorbs water and its handling and stability terms differ from Australian opal. | |||
| Mexico | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest Jan to Dec, arrival Jan to DecFire opal from Queretaro and Jalisco, in transparent orange and red body colours, shipping year round. |
| Brazil | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest Jan to Dec, arrival Jan to DecPiaui production in white and crystal material, shipping year round. |
| United States | Harvest | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Arrival | Harvest May to Oct, arrival Jun to NovNevada and Idaho production, with the working season limited by winter. | |||||
| Indonesia | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest Jan to Dec, arrival Jan to DecBanten production in wood opal and common opal, year round. |
| Peru | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest Jan to Dec, arrival Jan to DecBlue and pink common opal, shipping year round. |
| Madagascar | Harvest | Harvest | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Harvest and arrival | Arrival | Arrival | Harvest Apr to Oct, arrival Jun to DecCommon opal alongside the wider coloured stone output, accessible in the dry season. |
Windows outside this pattern trade on request, including forward commitments against a mine run, parcels already sitting in a cutting centre, and material held in a free trade zone or bonded vault.
Customs, packing and contract terms
Indicative terms for opal. Tariff classification is the importer’s responsibility and limits change, so confirm both against the destination customs authority and the current regulation before you fix a contract.
- HS heading7103.10 Precious and semi-precious stones, unworked or simply sawn or roughly shaped
7103.99 Semi-precious stones, otherwise worked - PackingSealed and numbered parcels under a valuation certificate. Never containerised.
- Container loadingNot containerised. Moves by insured secure courier or hand carry against a declared valuation, with customs presentation at both ends.
- Contract and arbitrationCIBJO Blue Book nomenclature, with a GIA, Gubelin or SSEF report where the value warrants it. Sale on viewed and approved parcel terms with weight and treatment disclosure. Arbitration under the rules of the World Federation of Diamond Bourses or the ICC.
- Destination limitsOrigin declaration and OECD due diligence for minerals from conflict affected and high risk areas, US OFAC sanctions on Burmese ruby and jade under the JADE Act, anti money laundering registration and reporting for dealers in precious stones, and full disclosure of heat, diffusion, fracture filling and any other treatment.
Common questions
What grades of opal does SIP Global trade?
We quote 42 published grades of opal, including Species - Opal, confirmed by gemmological testing, Type - Declared, as precious opal or common opal, Refractive index - Reported, Specific gravity - Reported, Hardness - Reported on the Mohs scale and Water content - Declared, as measured or as characteristic of the origin. Every grade is tied to a delivery point and a settlement route. Grades outside the published list are priced on request.
How is opal graded?
Opal is bought on the play of colour and the body tone, and on whether the piece is solid or assembled. The contract states the type, the body tone, the pattern, the assembly status and any treatment, because an assembled or treated stone is a different product at a different price. Grading runs on 6 systems: Species, variety and identification, Colour, Clarity and inclusions, Rough form, size and yield, Treatment and disclosure and Parcel, documentation and settlement.
Where does SIP Global trade opal?
We trade opal in Australia, Ethiopia, Mexico, Brazil, United States, Peru, Indonesia and Madagascar and 23 further markets. Origins and destinations outside this list trade on request. We are not limited to the locations shown.
When is opal harvested and when does it arrive?
Typical windows are Australia: harvest jan to dec, arrival jan to dec; Ethiopia: harvest oct to apr, arrival dec to jun; Mexico: harvest jan to dec, arrival jan to dec; Brazil: harvest jan to dec, arrival jan to dec; United States: harvest may to oct, arrival jun to nov. Harvest is when the lot is taken at origin, arrival is when a shipment from that origin lands in a consuming market. Windows outside this pattern, including carry, trade on request.
What is the HS code for opal?
Opal is normally classified under HS 7103.10 (precious and semi-precious stones, unworked or simply sawn or roughly shaped) and HS 7103.99 (semi-precious stones, otherwise worked). The heading follows the form the goods are in at the border, and national tariffs extend it beyond six digits, so confirm the full line with the destination customs authority before you fix a contract.
How do I get a price for opal?
Send the grade, the origin and the delivery window to the SIP Global desk. That is enough for a trader to come back with a level and a settlement route. 2 listed opal markets are published on this page, each with its full specification and terms. We take both sides, physical and financial, prompt to long dated.
Standards and data sources
The grading language on this sheet follows published standards. Trade volumes and tariff lines are public record. Verify anything here against the source.
- UN ComtradeOfficial international trade statistics by HS code
- ITC Trade MapBilateral trade flows and tariff data
- FAOSTATFAO production and trade series for agricultural commodities
Price this with our desk
Grade, origin and window if you have them. If what you are carrying does not fit the sheet above, describe it in your own words and a trader will take it from there.