Buying guide

Aquamarine

Unlike emerald, aquamarine is usually eye-clean, so clarity is assumed and colour carries the price. Deeper Santa Maria blue is worth several times a pale sky tone, and larger stones show colour better.

Aquamarine at a glance

Mineral family: Beryl
Chemical formula: Be3Al2Si6O18
Mohs hardness: 7.5 - 8
Refractive index: 1.577 - 1.583
Specific gravity: 2.72
Crystal system: Hexagonal
Colours: blue
Birthstone month: March
Anniversary: 19th
Typical treatment: Routinely heated to remove green and yellow tones, producing purer blue. The treatment is permanent and undetectable.
In stock now: 3 stones from $77.50

What drives the price

In one line: Colour depth, size (colour intensifies with size), clarity.

Treatment

Routinely heated to remove green and yellow tones, producing purer blue. The treatment is permanent and undetectable.

Any seller unwilling to state treatment in writing is telling you something. Every listing on this site states it.

Durability and daily wear

Durable and ultrasonic-safe when free of fractures. Warm soapy water is sufficient.

Mohs 7.5 - 8, hexagonal crystal system, specific gravity 2.72.

Tradition and meaning

A stone of calm, courage and clear expression. Traditionally the sailor's protective stone.

Birthstone for March. Associated with Pisces and Aries. Anniversary stone: 19th.

Frequently asked

Why is aquamarine usually pale?

Aquamarine's colouring agent, iron, produces a light tone in small sizes. Colour deepens visibly above roughly 5 carats, which is why large aquamarines look far more saturated than small ones cut from the same rough.

Is aquamarine the same as blue topaz?

No. Aquamarine is beryl, related to emerald, and its blue is natural or heat-refined. Blue topaz is a different mineral whose colour comes from irradiation. Aquamarine is considerably more valuable.

Is aquamarine good for engagement rings?

Yes, at 7.5-8 Mohs it is durable enough for regular wear, though it is softer than sapphire and shows scratches over decades. A protective setting is sensible.