Is black zirconium or platinum 950 harder wearing?

Black zirconium, at Mohs 8.5 against 4.5. Airborne dust contains quartz at Mohs 7, so anything below that scratches from ordinary wear alone.

Platinum 950, at 21.4 g/cm³ against 6.5. That is 3.3 times the weight, which is very obvious on the hand rather than a technicality.

No. Platinum 950 can be resized by any jeweller. Black zirconium cannot, so we replace it free for life instead.

Platinum 950, starting at £995 against £245. That is about 306% more before any stone or inlay.

Only Platinum 950. Black zirconium is not a precious metal, so no hallmark exists for it.

Comparison

Black zirconium or Platinum 950?

Black zirconium is meaningfully harder, so if your hands take a beating the choice is largely made for you.

	Black zirconium	Platinum 950
Surface hardness	Mohs 8.5	Mohs 4.5
Density	6.5 g/cm³	21.4 g/cm³
Resizable	Replaced free	Yes
Hallmarked	Not applicable	Yes
Hypoallergenic	Yes	Yes
Price from	£245	£995

What the difference actually feels like

Platinum 950 is 3.3 times the weight of black zirconium for the same ring. On paper that is a number; on the hand it is the difference between a ring you forget about and one you are aware of every time you move. Neither is better. It is worth knowing which you want before you spend anything.

Black zirconium sits at Mohs 8.5 against 4.5. Ordinary household dust carries quartz at Mohs 7, which is the line that matters: below it a ring collects fine scratches from nothing more than daily life. That is not a marginal difference between these two, it is the main one.

Platinum 950 can be resized and black zirconium cannot. Fingers change over decades, so this matters more than it seems at the point of buying. Our answer either way is that we cover it: a resize on one, a free replacement on the other, for as long as you own the ring.

The straight answer

Choose black zirconium if anyone who has had a plated black ring wear through, or if manual work.

Choose platinum 950 if a white metal that stays white, or if sensitive skin.

Still torn? The metal chooser asks six questions and picks one, and it will tell you if neither of these is right.

In both materials

Rings to look at

Multi toned

Relieved black

Black cut back to bright metal along both edges.

From £315 4 / 5 / 6 / 7 / 8 mm

Multi toned

Twin groove

Two tones divided by a V cut around the centre.

From £315 5 / 6 / 7 / 8 mm

Truly unique

Hammered black

Struck by hand, so the facets never land twice the same way.

From £330 6 / 7 / 8 mm

Common questions

Is black zirconium or platinum 950 harder wearing?: Black zirconium, at Mohs 8.5 against 4.5. Airborne dust contains quartz at Mohs 7, so anything below that scratches from ordinary wear alone.
Which is heavier?: Platinum 950, at 21.4 g/cm³ against 6.5. That is 3.3 times the weight, which is very obvious on the hand rather than a technicality.
Can both be resized?: No. Platinum 950 can be resized by any jeweller. Black zirconium cannot, so we replace it free for life instead.
Which costs more?: Platinum 950, starting at £995 against £245. That is about 306% more before any stone or inlay.
Are both hallmarked?: Only Platinum 950. Black zirconium is not a precious metal, so no hallmark exists for it.