Is 18ct gold or black zirconium harder wearing?

Black zirconium, at Mohs 8.5 against 3. Airborne dust contains quartz at Mohs 7, so anything below that scratches from ordinary wear alone.

18ct gold, at 15.6 g/cm³ against 6.5. That is 2.4 times the weight, which is very obvious on the hand rather than a technicality.

No. 18ct gold can be resized by any jeweller. Black zirconium cannot, so we replace it free for life instead.

18ct gold, starting at £795 against £245. That is about 224% more before any stone or inlay.

Only 18ct gold. Black zirconium is not a precious metal, so no hallmark exists for it.

Comparison

18ct gold or Black zirconium?

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

	18ct gold	Black zirconium
Surface hardness	Mohs 3	Mohs 8.5
Density	15.6 g/cm³	6.5 g/cm³
Resizable	Yes	Replaced free
Hallmarked	Yes	Not applicable
Hypoallergenic	Alloy dependent	Yes
Price from	£795	£245

What the difference actually feels like

18ct gold is 2.4 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 3. 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.

18ct gold 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 18ct gold if depth of colour, or if weight on the finger.

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

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

Plain

Court, 18ct

The same profile with twice the gold in it.

From £795 2 / 3 / 4 / 5 / 6 mm

Plain

D-shape, 18ct

Domed outside, flat inside. The traditional English profile.

From £845 2 / 3 / 4 / 5 mm

Multi toned

Two tone, 18ct

Two golds in one band, both of them solid.

From £950 3 / 4 / 5 / 6 mm

Common questions

Is 18ct gold or black zirconium harder wearing?: Black zirconium, at Mohs 8.5 against 3. Airborne dust contains quartz at Mohs 7, so anything below that scratches from ordinary wear alone.
Which is heavier?: 18ct gold, at 15.6 g/cm³ against 6.5. That is 2.4 times the weight, which is very obvious on the hand rather than a technicality.
Can both be resized?: No. 18ct gold can be resized by any jeweller. Black zirconium cannot, so we replace it free for life instead.
Which costs more?: 18ct gold, starting at £795 against £245. That is about 224% more before any stone or inlay.
Are both hallmarked?: Only 18ct gold. Black zirconium is not a precious metal, so no hallmark exists for it.