Sri Lankan White Sapphire

Buying this stone

Where it came from, what its weight band is for, and what to check before any money changes hands.

The deposit

Colourless corundum is one of Sri Lanka’s most abundant products, and most of it never reaches the market as white sapphire at all: it is the raw material the heat treaters buy to turn into blue and yellow. A stone that stays colourless and gets cut as itself has therefore been selected out of that flow for clarity, because there is nothing for an inclusion to hide behind in a colourless stone. That is the quiet reason a good white sapphire is harder to find than the price suggests, and why clarity rather than colour is the grading axis that matters here.

This stone

At 5.22 carats in a round brilliant this is sized and cut to sit where a diamond would, and it is worth being clear about what that does and does not give you. White sapphire has a lower refractive index and much lower dispersion than diamond, so it returns a cooler, glassier brightness instead of throwing coloured fire, and at this size the difference is visible rather than academic. What it does give you is corundum’s hardness of 9 for a fraction of the cost, which is why it holds a polish through years of daily wear where a softer colourless stone would go dull.

Treatment

Unheated and untreated. For colourless corundum this claim means something slightly different from what it means elsewhere in the catalogue: heat is used on this material to add colour, not to improve it, so an unheated white sapphire is one that was never a candidate for conversion. The material genuinely worth worrying about here is synthetic colourless corundum, which has been manufactured in quantity since the early twentieth century, is chemically identical, and costs almost nothing. That separation is a laboratory job, not an eye job.

The report

A IIGJ report is held for this 5.22 cts white sapphire and is handed over with it. Verify the number with the laboratory rather than only with us, and check its weight against the stone before money moves.

Before you pay

• Insist on a report identifying the corundum as natural. This is the one stone in the catalogue where your eye cannot do the work.
• If a colourless stone throws obvious rainbow fire, it is not sapphire. Cubic zirconia and moissanite are both far more dispersive.
• Look for a stone that is eye clean. In a colourless material every inclusion is on display.

Read next

Heera, the diamond covers the material itself and what gets sold in its place. How to buy a coloured stone covers pricing, treatment and reports.

Written by Kamal Kishore Agarwal, founder and gemmologist, Gem-A qualified, buying in Johari Bazaar since 2008.