Platinum purity outside jewelry is graded on three separate scales: bullion Good Delivery and futures fineness at 99.95% (0.9995), refined-metal ASTM grades, and industrial grades running as high as 99.9999% for research use. Which scale applies depends on whether the metal is traded as a bar, sold as refined sponge, or fabricated into foil and sputtering targets. This page works through each scale, then cross-references the separate, lower scale used for finished jewelry.
How Platinum Purity Grades Are Classified#
Platinum purity is classified into three regimes: jewelry fineness (parts per thousand), bullion and futures fineness (Good Delivery and IRA), and industrial and refined-metal grades (ASTM and supplier N-grades), each with its own minimum. This page continues the broader platinum purity overview, covering the scales that apply once platinum leaves the jewelry counter:
- Jewelry fineness: parts per thousand, such as 850, 900, 950 and 999, for finished rings and settings.
- Bullion and futures fineness: a 99.95% (0.9995) minimum, for Good Delivery bars, NYMEX-deliverable metal and IRA-eligible bullion.
- Industrial and refined-metal grades: ASTM sponge and bar grades plus supplier N-grades, from 99.85% foil up to 99.9999% research-grade metal.
Why Purity Is Reported by Difference, Not Measured Directly#
Refined platinum's purity is determined by difference from its measured impurities, not measured directly, because the impurities that matter most in platinum are the other platinum group metals, chemically nearest and hardest to separate. A laboratory measures rhodium, iridium, ruthenium, palladium, gold, silver and around eighteen further elements in a sample, then subtracts their combined total from 100%, under ASTM International's B561 specification for refined platinum. Rhodium, iridium, ruthenium and palladium head that list because they are hardest to separate from platinum, while contaminants such as lead, tin, zinc, iron, copper and arsenic matter because they embrittle the metal or poison downstream catalysts. A parallel purity-by-grade logic governs catalytic converter grades, where buyers price scrap against assayed content, not a flat rate.
Bullion and Investment Grades#
Good Delivery and futures-grade platinum trades at the live platinum spot price, since both grades set only a purity floor, not a separate price series. Current spot, futures and dealer levels for all six platinum group metals appear on DailyPlatinum's platinum group metal prices today page; this section addresses only the purity standards those quotes assume, not the number itself.
LBMA/LPPM Good Delivery: 99.95% Minimum#
LBMA/LPPM Good Delivery platinum requires a minimum purity of 99.95%, verified by a five-figure assay determination that must not be less than 99.950% and must agree with the referee's own determination. An assay reading between 99.946% and 99.949% is reported as 99.94%, never rounded up, a deliberately conservative rule that protects the floor rather than the applicant. Good Delivery plates and ingots weigh between 1 kg (32.151 troy oz) and 6 kg (192.904 troy oz), each stamped with the refiner's mark, a serial number and the month and year of production. Refiners of platinum bars sold to retail buyers must first hold Good Delivery or sponge accreditation from the London Platinum and Palladium Market.
NYMEX Futures and IRA Fineness: 0.9995#
NYMEX platinum futures require delivery of an approved plate or ingot at a minimum 99.95% purity (0.9995 fineness) in a 50 troy oz contract, and IRC §408(m)(3)(B) uses that same NYMEX delivery standard to set the fineness threshold for IRA-eligible platinum and palladium bullion at 0.9995 fine. Gold's IRA threshold sits lower, at 0.995 fine, so platinum and palladium face a stricter purity bar than gold inside a US retirement account, a consequence of the futures specification rather than an arbitrary choice. Eligible bars must come from a NYMEX/COMEX-approved or LBMA/LPPM-listed refiner, hallmarked at 0.9995 fine or better. Rhodium, iridium, ruthenium and osmium have no IRA route at all: Section 408(m)(3)(B) names only gold, silver, platinum and palladium.
ASTM Refined Platinum Grades#
ASTM International's B561 specification for refined platinum defines two grades, Grade 99.95 (UNS P04995) and Grade 99.99, covering platinum sponge, cast bar and wrought forms. The specification controls platinum against the same impurity list used to define purity by difference: the other platinum group metals, gold, silver and roughly twenty base-metal and metalloid elements. Platinum's 99.99% ceiling sits above rhodium's own ASTM specification, which tops out at Grade 99.95, a reflection of how much harder rhodium is to separate from the other platinum group metals. Standard commercial PGM sponge, the porous metal from hydrogen reduction of a precipitated salt, is sold at a minimum of 99.95% across platinum, palladium, rhodium, iridium and ruthenium alike.
Industrial and High-Purity Grades#
Platinum used outside jewelry and bullion is refined to industrial grades from 99.85% foil up to 99.9999% (6N) research-grade metal, chosen by application rather than by a single "purest" standard. A fabricator selecting sponge for catalyst production needs a different purity floor than a physicist selecting metal for a reference standard, so the grade ladder runs continuously rather than jumping straight from bullion fineness to research purity.
Platinum Foil: 99.85% to 99.999%#
Goodfellow's platinum foil catalogue lists purities from 99.85% to 99.999%, at thicknesses from 0.0005 mm to 2 mm. Thickness tolerance widens at the thinnest gauges, running ±25% below 0.01 mm and ±10% above 0.05 mm, while linear dimensions carry a tolerance of ±1 mm below 100 mm. Stock sizes range from 5 mm to 150 mm square, letting a buyer specify purity, thickness and sheet size independently rather than accepting one fixed catalogue item.
5N and 6N Platinum: Thin-Film and Research Grades#
Suppliers grade high-purity platinum as 99.999% (5N, up to 10 ppm impurities) for thin-film and reference-material use, and 99.9999% (6N, up to 1 ppm) for research and metrology, a grade rarely produced for other platinum group metals. The same N-grade convention applies to ruthenium sputtering targets, sold at a commercial 99.95% and a high-purity 99.995% or better, with alkali, alkaline-earth and transition metals each capped below 1 ppm.
| Grade | Purity | Typical impurity cap | Typical use |
|---|---|---|---|
| Foil (Goodfellow range) | 99.85% to 99.999% | Not separately specified by grade | General lab and fabrication foil, 0.0005-2 mm |
| 5N | 99.999% | Up to 10 ppm total | Thin-film deposition, semiconductor-adjacent use, reference materials |
| 6N | 99.9999% | Up to 1 ppm total | Research and metrology, rarely a real production grade outside platinum |
| Ruthenium sputtering target, high purity | 99.995%+ | Under 1 ppm per element (alkali, alkaline-earth, transition metals) | Hard-disk and thin-film sputtering targets |
Jewelry Purity Grades, for Comparison#
Jewelry platinum is graded on a different, lower scale than bullion or industrial platinum: hallmarking standards recognize 850, 900, 950 and 999 as legal fineness marks, well below the 99.95%-plus floors above. National grade sets vary:
- UK: 850, 900, 950 and 999, with 850 the minimum legal fineness.
- Japan: 1000, 950, 900 and 850, from bridal (950) to accessible chain product (850).
- China: 950, 900 and 850 under GB 11887-2012, with 950 dominant in bridal jewelry.
950 platinum is the dominant bridal grade in most Western and Chinese markets; 900 platinum is a legacy US and Japanese alloy, both governed by the platinum hallmarks framework.
| Scale | Grades | Minimum |
|---|---|---|
| Jewelry fineness | 850, 900, 950, 999 (UK) | 850 |
| LBMA/LPPM Good Delivery | Single bullion grade | 99.95% |
| ASTM refined platinum | Grade 99.95, Grade 99.99 | 99.95% |
| Industrial/research | Foil through 6N | 99.85% to 99.9999% |
Platinum Purity Grades FAQ#
What is the best grade of platinum?#
There is no single "best" platinum grade; Good Delivery (99.95%) is the standard for bullion, ASTM 99.99 for refined-metal supply, and 5N/6N grades for thin-film and research use. The right grade is the one specified for the application, not the highest number available.
How do I test platinum at home?#
Testing platinum at home, or by XRF or density measurement, is covered separately at how to test platinum; this page addresses which purity grade a piece is claimed to meet, not how to verify it.
What are platinum's symbol, atomic number and CAS number?#
Platinum has the symbol Pt, atomic number 78 and CAS number 7440-06-4, the identity behind every grade discussed above; see platinum (Pt), element 78 for its full properties.