Sapphire Buying Guide

A Guide to Buying Sapphire

Sapphire is the variety of corundum with a blue color. Red corundum is considered to be ruby; any other color is still termed sapphire but preceded by the color of the stone like green sapphire or yellow sapphire. It was most likely discovered in Sri Lanka (Ceylon), but since its discovery has also been found in Australia, Burma (Mogok), Cambodia, China, India (Kashmir), Kenya, Laos, Madagascar, Malawi, Nigeria, Rwanda, Tanzania, Thailand and the United States, primarily Montana. The name is believed to be derived from a Greek word for blue, “sappheiros.”

PGS342 - Medium to deep blue color sapphire. Lightly included but with quite good brilliancy. A rare find for this size, shape and color.

PGS347 - Incredibly intense blue on this sapphire. Outstanding!

PGS857 - Deep blue heart shape sapphire.

The primary factor in determining the value of a sapphire is its color. The ideal color would be an intense rich blue, a stone that is too light or too dark will have much less value. They are best viewed either in fluorescent light or daylight just after sunrise or before sunset, as sources with the least output in the red end of the spectrum are best. Incandescent light is the least preferable.

Sapphires tend to be cleaner than ruby in terms of clarity, so stones should definitely appear clean to the unaided eye. There are other cases where the inclusions such as extremely fine silk will increase the value of the stone, especially with the famous Kashmir sapphires which appear velvety. Too much silk however can detract from the color of the stone making it appear grayish which is undesirable. Fine star sapphires have sharp six or twelve rayed stars that should be centered well in the middle of the cabochon. The legs should be smooth and the stone should still have an intense blue color. Having a good star alone isn’t enough to be considered highly valuable.

Ovals and cushions are the most common cut for sapphires, although they can be found in other shapes including emerald, heart and round. Round sapphires are worth slightly more than the other shapes, but in any shape they shouldn’t be cut overly shallow or deep. Cabochons can also be found; but usually only in star sapphires or when the clarity isn’t good enough to facet.

Most sapphires you will find are heat treated to improve their appearance; this helps them become stable in color. Occasionally you will also see stones treated with dying, oiling, or surface diffusion. In smaller stones of lesser quality heat treated stones sell for the same amount as untreated stones, but in larger stones of finer quality an untreated stone can sell for 50% or more than a comparable treated stone. Synthetic sapphires also exist and sell for just pennies per carat.

Sapphire ranks up there with some of the world’s most expensive gems like emerald and ruby. The highest price ever paid for a sapphire was slightly over $3 million ($48,871/carat) for the 62.02 carat Rockefeller sapphire in 2001.

Sapphire Properties (A variety of corundum)

Composition	Al₂O₃
Refractive Index	1.762–1.770 (0.008) Uniaxial negative
Specific Gravity	4.00
Hardness (Mohs)	9
Crystal System	Hexagonal (trigonal)
Pleochroism	Strongly dichroic: violetish blue/greenish blue
Phenomena	6 or 12-rayed star
Colors	All except red (ruby)
Enhancements	Frequently heated; occasionally oiling, dying, surface diffusion
Handling	No special care needed
Synthetic available?	Yes