Sapphire

Sapphire is any form of gem quality corundum, other than red. It is the second hardest mineral on earth next to diamond. While blue is the most traditional and classic color for sapphire, sapphire is actually found in a variety of different colors. Most natural sapphire is quite pale and light in color.
 
Blue is the best-known of the sapphire colors. The prized Kashmir and Burmese sapphires have a deep blue that is intense and velvety. These sapphires are not often seen on the market today. Sri Lankan and Madagascar sapphires are the most common today, with a wide range of colors from light blue to dark blue. With blue sapphire, the intensity of blue is the most important factor. For example, a huge sapphire with a washed-out, weak blue color is much less valuable than a much smaller stone of excellent color.

An intense, rich pure cornflower blue that is not too dark or too 'inky' is the most desirable colour. Overall, sapphires that are too dark or too light in color are less valuable, but light-blue sapphires often have greater brilliance that is rarely found in darker blue stones. Colorless sapphires are actually quite rare, since most stones will exhibit some faint hints of color.

 Pink sapphire and purple sapphire are often colored by iron and titanium impurities. Most yellow sapphire is naturally on the lighter side. It is through heat treatment that a more intense yellow golden color is produced. Beryllium-treated sapphire may result in brilliant bright yellow. Small traces of iron can cause yellowish and greenish hues in stones. Chromium is known to produce fine pinks (and red in ruby), whilst iron and vanadium together can produce lovely orange stones. Padparadscha sapphire is a very rare sapphire with a pinkish-orange hue.