Blue Gemstone Jewellery: Six Blues and How to Tell Them Apart

Blue is the colour people ask for most often and describe least precisely. "Something blue" covers stones with almost nothing in common beyond the word: opaque and transparent, ancient and recently discovered, twenty pounds and two thousand.

Six blues worth knowing, what separates them, and how to choose.

The six at a glance

Hardness figures are measured values on the Mohs scale. The "best for" column is our judgement based on how these stones behave in wear, not a technical rating.

The stones

Lapis lazuli

Lapis is opaque, deep royal blue, scattered with small gold flecks of pyrite. It does not sparkle so much as glow flatly, like painted colour.

It is a rock rather than a single mineral: lazurite for the blue, calcite for the white veining, pyrite for the gold. Ground to powder it produced ultramarine, the pigment that cost more than gold in Renaissance Europe.

Choose it for colour with history behind it, worn in earrings or a pendant rather than a ring. One styling note: lapis suits gold, because the pyrite flecks are gold-toned and a gold setting picks up what is already in the stone.

Turquoise

Turquoise is the only blue here that leans green and reads as warm. Opaque, usually with brown or black veining running through it.

It is porous, which is why most turquoise on the market is stabilised with resin to make it wearable, and why untreated turquoise gradually deepens in colour as it absorbs skin oils over years.

Choose it if you want blue that works with summer clothes and tanned skin, and you like stones with visible character. It also suits gold better than silver, which pushes it towards a Southwestern look.

Iolite

Iolite is transparent violet-blue and changes colour depending on the viewing angle. Held one way it reads as deep sapphire blue; turned, the colour lightens or drains away almost entirely.

That property is pleochroism, and it earned iolite the old trade name water sapphire. At 7–7.5 it is harder than most people expect and wears well.

Choose it if you want sapphire's colour without sapphire's price, and find the shifting quality interesting rather than inconvenient.

Aquamarine

Aquamarine is pale, transparent, and always leans slightly green rather than violet. That is the quickest way to identify it.

At 7.5–8 it is the second-hardest stone here and genuinely suitable for daily wear, including rings, which is unusual among coloured stones. Its colour deepens with size, so small aquamarines are naturally pale. That is a matter of physics rather than quality.

Choose it if you want something you can wear without thinking about it.

Tanzanite

Tanzanite is transparent violet-blue, found in one small area of Tanzania and nowhere else. It was discovered in 1967, making it the newcomer here by several thousand years.

It is pleochroic like iolite, showing violet, blue and often a burgundy flash from different angles, and nearly all of it is heat-treated to reach that colour. It is also relatively soft for its price, around 6–7, with cleavage.

Choose it when the piece needs to feel like an occasion, and it will not be knocked about.

Sapphire

Sapphire is corundum, 9 on the Mohs scale, second only to diamond. That hardness is the real argument for it: sapphire is one of very few coloured stones that survives daily wear on a hand for decades.

Almost all sapphire is heat-treated, which is standard and permanent.

Choose it if you are buying one blue piece for life. Otherwise iolite or aquamarine give you the colour for a fraction of the cost, honestly described as what they are.

Which blue should you choose?

For everyday wear with no thought required, aquamarine or iolite are hard enough to forget about.

For maximum colour at the lowest cost, lapis.

For warmth and summer, turquoise.

For a piece that feels significant, tanzanite.

For one ring worn for decades, sapphire.

For a September birthday on a budget, lapis or iolite, both of which are traditional alternatives to sapphire.

You can see our current blue pieces in the Endless Blue Gemstone jewellery collection.

Frequently asked questions

What is the most affordable blue gemstone?

Lapis lazuli and iolite are both considerably less expensive than sapphire or tanzanite, and both are genuine natural stones rather than imitations.

Which blue gemstone is hardest?

Sapphire, at 9 on the Mohs scale. Aquamarine follows at 7.5–8, then iolite at 7–7.5. Lapis and turquoise are the softest here, at 5–6, and need more care.

What is a good alternative to sapphire?

Iolite is the closest visually and has been called water sapphire for centuries. Lapis lazuli is a traditional alternative September birthstone in its own right, and tanzanite offers a rarer violet-blue.

Why is my aquamarine so pale?

Aquamarine's colour intensity increases with size, so small stones are naturally light. A small stone showing deep saturated blue at a low price is more likely to be blue topaz or treated material.

Which blue stones can be worn every day?

Aquamarine, iolite and sapphire handle daily wear well. Lapis, turquoise and tanzanite are softer and better suited to earrings and pendants than to rings.

Does turquoise really change colour over time?

Yes, gradually, as its porous surface absorbs skin oils and lotions. Stabilised turquoise changes far more slowly. Many owners regard the resulting patina as a feature rather than a fault.