A mined sapphire and a laboratory-grown sapphire are the same material: corundum, crystallised aluminium oxide, nine on the Mohs scale of hardness, identical in composition, colour and brilliance. One formed in the earth over millions of years; the other is grown above ground over weeks. A blue crystal is a different material altogether, a cut glass that often carries the colour name “sapphire” and has a sparkle all its own.
The sapphires that make records
Sotheby’s has looked back at the five most valuable sapphires it has sold, and the list reads like a map. At the top sit the Richelieu Sapphires, a pair of Kashmir stones of 26.66 and 20.88 carats that sold for $8.4 million in 2013; beside them a 114.739-carat sapphire from Mogok in Burma, offered unmounted, which reached $7.2 million the same year. Every stone on the list is unheated, and every one is known by where it was found. Kashmir sapphires were mined for only a few years in the 1880s, and the velvety cornflower blue they are famous for has become the measure against which every blue sapphire is judged. At this level a sapphire is valued for its history as much as its colour: its origin, its untouched state and the hands it has passed through.
The sapphires grown above ground
Corundum was first grown in a laboratory in 1902, when the French chemist Auguste Verneuil published the flame-fusion method that still carries his name. A laboratory-grown sapphire is a sapphire in every respect a gemmologist measures: the same chemistry, the same crystal structure, the same hardness. It takes the same polish and holds the same colour by daylight and by candlelight. What changes is the scale within reach. A royal blue or cornflower sapphire of thirteen carats is a stone the earth yields so rarely that the salerooms record each one by name. Grown, a stone of that size can be cut for colour and presence first, and set as a ring to be worn every day.
The blue of a crystal
Crystal is cut glass, brightened by its formula and by the precision of its faceting. Swarovski, the best-known name in crystal, uses “Sapphire” and “Dark Sapphire” as the names of blue shades in its range, much as a paint chart borrows the names of flowers. Crystal sits between six and seven on the Mohs scale and throws a lively, rainbow sparkle. The name describes its colour; the material is its own.
At a glance
Mined sapphire: corundum, formed in the earth, nine on the Mohs scale. Valued by origin, treatment, colour and size.
Laboratory-grown sapphire: corundum, grown above ground, nine on the Mohs scale. Identical in composition to a mined sapphire.
Blue crystal: cut glass, six to seven on the Mohs scale. “Sapphire” names the colour.
The sapphires of The Bardot Collection
The sapphires of The Bardot Collection are laboratory-grown corundum, chosen for colour and cut at a scale the salerooms reserve for their most celebrated lots. The six emerald-cut sapphires each weigh thirteen carats: The Sovereign in royal blue, The Celeste in cornflower blue, The Olivine in olive green, The Florentine in canary yellow, The Peony in fancy pink and The Padparadscha in pink-orange. The Rosalind, a pink champagne sapphire, weighs sixteen. Each is set in hallmarked platinum, made individually in Britain and independently authenticated by a jeweller qualified with the Gemological Institute of America and the Gemmological Association of Great Britain.
Every piece is shown in detail by private video appointment, from wherever you are in the world.
