Alexandrite is a birthstone for June, along with pearl and moonstone. It is also the gem for the 55th wedding anniversary.
Described by some as "emerald by day, and ruby by night" it is a rare color change variety of the mineral chrysoberyl. Originally discovered in Russia's Ural Mountains in the 1830's, it is now found in Sri Lanka, East Africa and Brazil, but fine material is extremely rare and valuable... much more so than any other gemstone.
Alexandrite has rare, chameleon-like qualities. Its color can be a beautiful green in daylight or fluorescent light, changing to brownish or purplish red in incandescent light. This is a result of the complex way the mineral absorbs light.
You can also purchase created alexandrite, which are some of the more valuable synthetic gemstones, yet they are not close in the per carat value of a natural alexandrite.
Alexandrite is usually found in sizes smaller than five carats. Sizes over five carats are usually considered large and will command a proportionally higher price. In Ceylon, some of the largest alexandrite in the world are found, some weighing up to 60 carats each. These stones are of a darker color. Alexandrite is a hard, durable stone, rating an 8 ½ on the hardness scale.
So, if you are looking for a June birthstone that is more durable than a pearl or moonstone, look at an alexandrite. At any size, it is an unusual stone that can hold its value.