Apatite

Apatite, a stone seldom found in jewelry stores and virtually unknown to the general public, is beloved by collectors for its many different colors and forms. Only with the recent availability of the neon blue-green variety from Madagascar, has its jewelry use increased. The color of the best specimens of this type rivals the famed Paraiba tourmalines, but alas, this gem lacks their toughness and hardness. At 5 on the Mohs scale, apatite must be cut, set, and worn gently. Earrings, pendants, pins, and tie tacks are probably safe, but ring use should be limited to occasional wear pieces with protective settings. Care for this stone is similar to that given opals, it is heat and shock sensitive, so steamers and ultrasonics must be avoided.
 Gems are available in yellows and various shades of blues and greens. Some of the blues show chatoyancy and can be cut as cat's eyes. Main sources are Brazil, Canada, India, Mozambique, and Madagascar.

The major sources listing values for gems do not yet catalog the blue-green variety so I have extrapolated from the data available on the other colors. Sinkankas lists fine blue stones of between .5 to 1.5 ct at $75 to $200 per carat. His estimate for blue Brazilian stones is $100/ct. The rarest of all varieties, a rich purple from Maine, tops the list at $250 per carat.
 The degree of polish can vary on this soft stone due to skill levels of individual cutters, giving well polished stones premium value. As with most gems, saturation of color, size, and clarity are the major determiners of value.