Your buyer abroad asked for carbon data. Find where it sits in one carat or gram.
Pick what you make. The loupe shows where the carbon sits, what your buyer will ask for, and what you can safely say.
Gems and jewellery are not goods under the European Union’s Carbon Border Adjustment Mechanism (CBAM). This is a buyer request, not a border rule. Every example here uses the India grid factor: 0.675 kg of carbon dioxide (CO2) per kilowatt hour (kWh), financial year (FY) 2025-26.
What do you make?
- Lab-grown diamond
- Polished natural diamond
- Coloured gemstone
- Gold jewellery
- Silver jewellery
Lab-grown diamond: Reactor electricity drives it
Reactors and presses run hot and for weeks. Chemical vapour deposition (CVD) reactors and high pressure high temperature (HPHT) presses both burn electricity long.
Example month. kg of carbon dioxide (CO2) per polished carat.
- Growing: reactor electricity: 192.9
- Cutting and polishing energy: add yours
Reactor electricity drives the result. Use metered data, not published averages.
Example: 2,00,000 kilowatt hours (kWh) for 2,000 rough carats is 100 kWh a carat. 100 x 0.675 = 67.5 kg CO2 per rough carat, at the India grid factor of 0.675 kg CO2 per kWh for financial year (FY) 2025-26. At 35% yield, 67.5 / 0.35 = 192.9 kg per polished carat, before polishing energy. The kWh and yield are example values.
What your buyer will ask
- kWh from reactor or press meters, not nameplate ratings.
- Rough carats grown in the same period.
- Yield from rough to polished.
- Which grid factor, and which FY.
- Chillers, compressors and vacuum pumps that keep growth running.
- Failed runs stay in. Their energy belongs to the carats that came out.
What you can safely say
- Safe to say: “Laboratory-grown diamond. [Your figure] kg CO2 per polished carat, reactor electricity only, from metered readings, India grid factor 0.675 kg CO2 per kWh, FY 2025-26.”
- Safe to say: A lower figure from renewable power, only with a contract or certificate behind it. Report the grid figure too.
- Not on its own: “Sustainable” or “eco-friendly”. Since 27 September 2026, the European Union treats generic claims like these as an unfair practice unless the seller can show recognised excellent environmental performance. In the United States, the Federal Trade Commission treats unqualified claims as hard to back.
- True, but not enough: “No mining.” It does not make the stone sustainable. Always call the stones laboratory-grown.
What this leaves out
Hydrogen and methane gas for CVD, graphite and catalyst for HPHT, and seed plates bought from others come from supplier figures. Generator diesel during outages counts at 2.68 kg CO2 per litre. Nothing here is verified. Only an independent verifier can verify a figure.
Polished natural diamond: In this example your factory is the smaller part
Two parts: your factory, and the rough you cut from.
Example month. kg of carbon dioxide (CO2) per polished carat. The rough part is CO2 equivalent (CO2e).
- Your factory: electricity and generator diesel: 14.17
- Rough: example placeholder, 50 kg per carat recovered, scaled for weight lost: 125
Report the factory part and the rough part separately, each with its source.
Example: 40,000 kilowatt hours (kWh) x 0.675 = 27,000 kg CO2, plus 500 litres of generator diesel x 2.68 = 1,340 kg. That is 28,340 kg over 2,000 polished carats, 14.17 kg a carat, at the India grid factor of 0.675 kg CO2 per kWh for financial year (FY) 2025-26. Rough used: 5,000 carats, so 2.5 rough carats per polished carat, and 50 x 2.5 = 125 kg CO2e. The 50 kg per carat recovered is an example placeholder, not any miner’s number. Total in this example: 139.17 kg CO2e per polished carat.
What your buyer will ask
- Factory energy per polished carat, and the period.
- The yield you used.
- The miner’s published figure for the year your rough came from. Quote the report edition and say it is self-reported.
- A stated average labelled as an estimate, if your rough came through traders and the source is unknown.
What you can safely say
- Safe to say: Cutting and polishing and the rough, as two figures, each with its source, the yield and the period.
- Avoid: One blended figure on a tag. Claims need to be specific and backed by evidence.
- Not a carbon figure: A Kimberley Process certificate. It gives the country of origin of a parcel, nothing more.
What this leaves out
Mining and rough supply are usually far larger than polishing. Label a polishing-only figure as the polishing step only.
Coloured gemstone: Wheels, laps and a generator
Cutting wheels, polishing laps, sorting lights and air conditioning.
Example month at a Jaipur cutting unit. kg of carbon dioxide (CO2).
- Electricity: 2,500 kilowatt hours (kWh): 1,688
- Generator diesel: 100 litres: 268
- Rough stone: ask your supplier
0.078 kg CO2 per finished carat in this example. Divide by finished stones, not rough weight.
Example: 2,500 kWh x 0.675 kg CO2 per kWh (India grid factor, financial year (FY) 2025-26) = 1,688 kg. Diesel 100 litres x 2.68 = 268 kg. Total 1,956 kg over 25,000 finished carats is 0.078 kg per carat. Quantities are example values.
What your buyer will ask
- A figure per finished carat, from your bills and finished stock register.
- Electricity and generator diesel for the month.
- Rough stone: your supplier’s data, or a stated estimate.
- Stones sent to outside cutters: their kWh per lot, or a split by carats.
What you can safely say
- Safe to say: “Cutting and polishing only. [Your figure] kg CO2 per finished carat, from our bills for [month].”
- Not yet: A figure that sounds like the whole stone. The rough stone and its mining sit with your supplier’s data.
What this leaves out
Yield from rough to finished is often low, so the rough stone carries most of any upstream footprint.
Gold jewellery: Mined or recycled swings it
Flip the gold. Watch the casting furnace and torches become the bigger part.
Example: a 10 gram, 22 karat chain. kg of carbon dioxide equivalent (CO2e).
- Gold: 9.16 g of fine gold, example placeholder gold factor: 183.2
- Workshop energy: 1.10
- Gold: 9.16 g of fine gold, example placeholder gold factor: 0.92
- Workshop energy: 1.10
Mined gold: the metal is almost the whole figure. About 184.3 kg CO2e in this example.
Recycled gold: your workshop is the bigger part. About 2.0 kg CO2e in this example.
Example workshop month: 3,000 kilowatt hours (kWh) x 0.675 = 2,025 kg of carbon dioxide (CO2), at the India grid factor of 0.675 kg CO2 per kWh for financial year (FY) 2025-26, plus liquefied petroleum gas (LPG) 60 kg x 2.98 = 178.8 kg. Total 2,203.8 kg over 20,000 g dispatched is 0.110 kg per gram. Both gold factors (20 mined, 0.1 recycled kg CO2e per gram) are example placeholders, not real factors. Use your refiner’s figure and its year.
What your buyer will ask
- Grams of fine gold, not grams of jewellery. 22 karat is 91.6 percent gold.
- Mined and recycled shares, with the refiner’s statement and bar or lot numbers that match your invoices.
- The gold factor’s source name and year. A number from a news story is not a source.
- Workshop energy for the period, per gram of finished piece.
What you can safely say
- Safe to say: “Recycled” only when the supplier’s documents say so, or the recycled share of a mixed lot.
- Treat as mined: Gold bought from a bank or bullion dealer, unless the refiner says otherwise.
What this leaves out
Inside the workshop: burnout ovens, induction casting machines, torches, polishing motors. Example: 3,200 kWh and 120 kg LPG for 2,500 pieces is 1.007 kg CO2 per piece. Metal recovered from dust and sprues goes back into production, so do not count it as a new purchase twice.
Silver jewellery: The allocation choice dominates
Most silver is a by-product of lead, zinc, copper or gold mining. The mine’s emissions have to be split.
Example only. kg of carbon dioxide (CO2) per kg of jewellery, workshop part.
- Silver metal: from a published source
- Workshop electricity: 81.0
- Workshop gas (liquefied petroleum gas, LPG): 8.9
Splitting a mine’s emissions by mass or by value can change the silver figure by about 200 times. Write the method beside the number.
Example mine: the same mine, split two ways, gives silver figures about 200 times apart. Example workshop: assumed 120 kilowatt hours (kWh) x 0.675 = 81.0 kg CO2, at the India grid factor of 0.675 kg CO2 per kWh for financial year (FY) 2025-26, plus 3 kg LPG x 2.98 = 8.9 kg. All mine figures and workshop inputs are example values, not real data. Use a published silver source and copy its stated method.
What your buyer will ask
- Silver per kg of product, with the source, year and allocation method.
- Share of recycled silver, and how you know it, such as refiner certificates.
- Workshop energy per kg, from your own bills.
- Plating metals such as rhodium listed separately. Their factors are very high per kg.
What you can safely say
- Safe to say: The method written beside the number: “by mass” or “by economic value”.
- Not new silver: Your own casting and filing scrap, sent back for refining and reused.
What this leaves out
Recycled silver usually carries only collection and refining. Silver bought as bullion often mixes mined and recycled sources, so ask the refiner what share is recycled.
Same grid factor, wherever you work
Pick your cluster. Each line is the same sum on your own bills.
Surat
Diamond units: kilowatt hours (kWh) on the electricity bill times 0.675 kg of carbon dioxide (CO2) per kWh, financial year (FY) 2025-26. Divide by carats polished.
Example: 12,000 kWh x 0.675 = 8,100 kg CO2, over 400 carats is 20.3 kg CO2 per carat. That covers your electricity only. Mining and rough supply sit outside it.
Jaipur
Gold, silver and gemstone makers: buyers usually want workshop electricity and liquefied petroleum gas (LPG), plus a figure per piece or per gram.
Precious metal dominates, so they care where gold and silver come from and whether recycled content is backed by supplier documents.
SEEPZ Mumbai
Santacruz Electronics Export Processing Zone (SEEPZ) is a special economic zone (SEZ). Power drawn there is still Indian grid power: 0.675 kg of carbon dioxide (CO2) per kilowatt hour (kWh), financial year (FY) 2025-26.
A lower figure needs renewable certificates or a green tariff in your name. Gold and diamonds you buy are separate purchases, not your electricity.
Thrissur
Gold workshops: electricity at 0.675 kg of carbon dioxide (CO2) per kilowatt hour (kWh) plus liquefied petroleum gas (LPG) at 2.98 kg CO2 per kg. Divide by grams finished.
Example: 900 kWh x 0.675 = 607.5 kg, plus 60 kg LPG x 2.98 = 178.8 kg. That is 786.3 kg over 4,000 g, 0.197 kg CO2 per gram, about 0.20. That is the making stage only. The gold is a separate and far larger figure.
Buyer sent a questionnaire?
See which answers your electricity bills and fuel invoices already fill. See the buyer questions or pick your market
Senseible reads your bills into a record for the making stage. It does not vouch for marketing claims.