The name PT950 sounds precise — and it is. It means the metal is 95% pure platinum. But that leaves 5% unaccounted for, and many buyers wonder what the rest is and why pure platinum is not used on its own. The answer is a small but deliberate alloying choice that makes platinum actually usable in jewelry. Understanding it helps you judge quality and ask the right questions when buying platinum.
Why Not Use 100% Pure Platinum?
Pure platinum (999.5 fine) is very soft. Like pure gold, it is too malleable to hold a setting securely or survive daily wear without deforming. A ring cast in pure platinum would bend easily, and its prongs would not grip a diamond. Jewelry metals are always alloyed — gold with copper and silver, platinum with small amounts of other platinum-group metals — to add hardness and durability while keeping the metal precious.
What Is in the 5%?
PT950 is alloyed most commonly with copper, cobalt, iridium or ruthenium. These small additions harden the platinum enough to set stones and hold a band’s shape, while leaving the metal predominantly platinum. The choice of alloy affects slight variations in hardness and how the metal polishes, but to the wearer the result is the same: a dense, pure-white, hypoallergenic ring. The hallmark “PT950” guarantees the platinum content regardless of which alloy was used.
How Alloy Affects Setting and Durability
The 5% alloy is exactly what lets a platinum ring hold prongs that stay tight for decades. Pure platinum would spread and loosen. The alloyed version has the structural stiffness needed for a durable setting. This is why platinum, despite being a soft precious metal, is prized for engagement rings: it is hard enough to hold a stone securely, yet dense and pure enough to feel luxurious.
Reading the Platinum Stamp
Real platinum jewelry is stamped “PT950” or “PLAT 950.” Be wary of pieces stamped only “PT” without a number — that is not a reliable purity mark. Like gold hallmarks, the numbered stamp is the guarantee. Our PT950 range carries the proper stamp, and we provide assay documentation for bulk orders. If you want to learn more about how precious metals are tested, our quality page explains the inspection process.
Frequently Asked Questions
Is PT950 still pure platinum? Yes — 95% platinum is considered high-purity and is the standard for fine jewelry.
Does the alloy make it less hypoallergenic? No — the added metals are platinum-group elements and do not contain nickel.
Is 999 platinum better than 950? Not for jewelry — 999 is too soft to set stones durably.
Why does my platinum ring have other stamps? Maker’s marks and assay office marks appear alongside PT950; all are normal.
How to Confirm You Are Buying Real PT950
Because platinum carries a premium, it pays to verify. Start with the stamp: a genuine piece carries “PT950” or “PLAT950”, clearly and crisply struck. Be cautious of pieces stamped only “PT” with no number, or pieces where the mark looks laser-etched and shallow. Weigh the ring: platinum feels noticeably denser than a similar gold ring. If a deal seems too cheap for a platinum piece, it probably is. Reputable sellers provide assay paperwork and are happy to show the stamp up close. When you buy from us, every platinum piece carries the proper stamp and documentation, and we walk you through reading it so you can verify for yourself.
PT950 in Everyday Jewelry Design
The alloy in PT950 is what makes the metal so versatile for settings. It is stiff enough to hold delicate prongs yet soft enough to shape by hand. That balance is why platinum has long been the setting metal of choice for important engagement rings — it grips stones securely and wears without thinning. Whether the design is a simple solitaire or an intricate pavé band, the same 95% pure alloy delivers both luxury and structural confidence.
The Difference Between Cobalt and Iridium Alloys
PT950 is not a single recipe; the 5% alloy can be cobalt, iridium, ruthenium or copper, and each gives the metal a slightly different character. Cobalt-alloyed platinum is harder and takes a brighter polish, which is why it is common in mass-produced bands. Iridium-alloyed platinum is denser and more rigid, favored for fine and heirloom settings where maximum prong strength matters. Copper-alloyed platinum has a slightly warmer tone and is easier to cast in intricate designs. To the everyday wearer these differences are subtle, but they explain why two PT950 rings can feel slightly different even though the stamp is identical.
For buyers, the practical takeaway is that “PT950” guarantees purity but not a single manufacturing recipe. That is normal and not a reason to distrust a piece. What matters is that the stamp is genuine, the weight feels right, and the setting is well made. If you have a specific preference — a bright polish, maximum prong rigidity, or a warmer tone — ask which alloy your maker uses. Our platinum collection uses a consistent, controlled alloy, and we provide assay documentation with bulk orders.
Platinum vs White Gold: The Alloy Story Explains the Price
The price gap between platinum and white gold is partly explained by how each is made. White gold starts as yellow gold alloyed with white metals, then rhodium-plated to achieve its bright color. Platinum is already naturally white and needs no plating, but it is denser and rarer, and it requires higher casting temperatures and more specialized labor. So white gold costs less partly because it relies on a plating finish, while platinum costs more because the whole piece is solid, dense, naturally white metal. Over decades, white gold needs periodic replating; platinum does not. When you look at the long-term cost of ownership, the initial gap narrows. Read our comparison guides in the education section for the full breakdown.
How to Confirm You Are Buying Real PT950
Because platinum carries a premium, verify before you buy. Look for a crisp, properly struck "PT950" or "PLAT950" mark. Be cautious of pieces stamped only "PT" with no number, or marks that look shallow and laser-etched. Weigh the ring; platinum feels noticeably denser than a similar gold ring. If a price seems too cheap for platinum, it probably is. Reputable sellers provide assay paperwork and show the mark up close. Every platinum piece we sell carries the proper stamp and documentation, so you can verify with confidence.
