The majority of blue spinel has a
significant grey mask and hence lacks the blue hue of a fine sapphire. This, combined
with the fact that spinel is significantly less popular than sapphire, results in a
lower overall price. However, the benefits of spinel are its rarity of treatment (it is
occasionally heated or fracture filled), and its exceptional luster, fire, and
durability. It has a high refractive index. Due to these factors, some people ignore the
greyer colour, particularly in a well-cut spinel.
Additionally, they lack
the zoning that sapphires exhibit. This has resulted in extremely high prices for
unheated sapphires - especially since the emergence of the Kate/Diana ring.