September has arguably the best birthstone of the twelve. Sapphire is a deep, velvety blue, it carries centuries of association with wisdom and loyalty, and, unusually, it is tough enough to wear every day for a lifetime without a moment's thought. At 9 on the hardness scale it is beaten only by diamond.

There is also more to it than blue, which surprises most people. This guide covers how to wear a September birthstone, the full range of sapphire colours, what to look for when buying, and where lapis lazuli, September's older alternative, fits in. For every month and stone, see our birthstones by month chart.

Three ways to wear a September birthstone

As a piece in its own right, and genuinely for ever. A sapphire pendant or ring is the birthstone equivalent of a good coat: buy once, wear for decades. Because it is so hard, a sapphire ring survives everything a hand does to it, and the deep blue is rich enough to carry a whole look while still reading as classic rather than showy.

Set small into something personalised. A small sapphire beside an initial, set into an engraved tag, or as a charm on a bracelet. Blue is the most universally liked colour in jewellery, so this is one of the safest birthstones to choose when you are buying for someone else. It is also the natural way to mark more than one person, a stone each for your children along a single bar or tag.

Layered and stacked. Deep blue against plain gold is one of the great combinations, and because sapphire is so durable you can wear it in a stack without worrying about the stones knocking together. A sapphire eternity band between plain gold rings is a particularly good use of the colour.

Styling sapphire with your everyday gold

Yellow gold against deep blue is the richest, warmest pairing and the one that reads most timeless. It is how sapphires were set for centuries before white metals became fashionable, and it flatters a slightly darker or inkier stone particularly well by lending it warmth.

White gold is the crisper, more formal choice and the one most associated with sapphire engagement rings. It lets the blue read cool and jewel-like, and it suits a bright cornflower stone especially well, where you want nothing warming the colour.

Rose gold is the least conventional and rather lovely with pink or peach fancy sapphires. With a classic blue it creates a warm-cool contrast that feels modern rather than heritage.

Sapphire is not only blue

Here is the fact that surprises almost everyone: sapphire occurs in every colour except red. Pink, yellow, green, peach, violet and even completely colourless sapphires all exist, and are known collectively as fancy sapphires. The reason red is excluded is simply naming convention, red corundum is called ruby, and everything else of the same mineral is called sapphire.

The rarest and most coveted of the fancies is padparadscha, a delicate pink-orange named after the lotus flower, which can outprice fine blue material. For a September birthstone, a fancy sapphire is a lovely way to have the month's stone in a colour that suits you, while keeping all of sapphire's toughness. A white sapphire, incidentally, makes a convincing and far more affordable stand-in for a diamond.

What to look for in a sapphire

The great majority of sapphires are heat-treated, and have been for a very long time. Heating improves colour and clarity permanently, and it is entirely standard and accepted across the trade. Genuinely untreated sapphires of fine colour are rare and command a substantial premium, so if a stone is described as untreated it should come with a certificate and a price to match.

Colour matters more than size. The most desirable blue is a vivid, velvety cornflower, neither so dark that it looks black in low light nor so pale it looks washed out. Always view a sapphire in daylight and in lamplight before deciding, because some stones close up and go inky indoors, which is the commonest disappointment with a blue stone.

You may hear origin names used as shorthand for quality: Kashmir for legendary velvety blue, Ceylon (Sri Lanka) for bright lively stones, Burma for rich royal blue. They carry real premiums, but judge the stone in front of you rather than the label attached to it.

Wisdom, loyalty and truth

Sapphire has meant wisdom, loyalty and truth for as long as it has been worn. Medieval clergy wore it as a symbol of heaven, and it was believed to guard against envy and to reveal deceit. That association with fidelity is exactly why it has become such a natural choice for engagement rings, quite apart from its hardness.

It is also the stone of the fifth and forty-fifth wedding anniversaries, which makes a sapphire piece an easy and meaningful gift well beyond September birthdays.

Lapis lazuli, September's older stone

Before sapphire settled into September, the month's stone was lapis lazuli, and it remains a traditional alternative. It is an opaque, intense ultramarine blue, usually flecked with gold pyrite, and it is one of the oldest treasured stones in human history: mined in Afghanistan for over 6,000 years, set into Tutankhamun's burial mask, and ground into the pigment ultramarine that Renaissance painters reserved for the Virgin's robes because it cost more than gold.

Where sapphire is transparent and precious, lapis is dense, matt and ancient-feeling, and it makes a completely different kind of piece. It is much softer, at 5 to 5.5, so it belongs in pendants and earrings rather than rings. Explore our lapis lazuli jewellery if that is the September blue you prefer.

Caring for sapphire

Sapphire is about as low-maintenance as a gemstone gets. Warm water, mild soap and a soft brush will keep it bright, and it is hard enough to shrug off ordinary knocks and scratches. Like diamond, it attracts grease, so if it looks lifeless it almost certainly wants a clean rather than repair. Ultrasonic cleaners are generally safe for untreated and heat-treated stones, though not for any stone that has been fracture-filled, so check first. Store it separately, because at 9 it will happily scratch nearly everything else in your jewellery box. Lapis, by contrast, needs the gentler treatment given to soft stones: a dry cloth, and no chemicals.

September birthstone questions

What is the September birthstone?

September's birthstone is sapphire, traditionally the deep blue variety, associated with wisdom, loyalty and truth. Lapis lazuli is September's older traditional alternative, an opaque ultramarine blue flecked with gold pyrite.

Do sapphires only come in blue?

No. Sapphire occurs in every colour except red, including pink, yellow, green, violet, peach and colourless. These are called fancy sapphires. Red corundum is simply called ruby instead. The rarest fancy is padparadscha, a pink-orange stone that can outprice fine blue sapphire.

Is sapphire good for everyday jewellery?

Exceptionally. At 9 on the Mohs scale sapphire is second only to diamond in hardness, so it can be worn daily in a ring indefinitely without special care. It is the most practical coloured stone on the birthstone calendar.

Are sapphires heat-treated?

Most are. Heating improves colour and clarity permanently and is a long-established, accepted practice across the trade. Untreated sapphires of good colour are rare and carry a significant premium, and should come with certification.

Is sapphire the same mineral as ruby?

Yes. Both are corundum. Red corundum is called ruby and every other colour is called sapphire, which is why the two share the same exceptional hardness of 9 and the same suitability for everyday wear.

What is lapis lazuli?

Lapis lazuli is an opaque deep-blue rock, usually flecked with gold-coloured pyrite, and September's traditional alternative birthstone. Mined in Afghanistan for thousands of years, it was once ground to make ultramarine pigment, which cost more than gold. It is soft at 5 to 5.5, so it suits pendants and earrings rather than rings.