Alexandrite is on of three birthstones for June (the other June birthstones are pearl and moonstone). It is the color-change variety of the mineral, chrysoberyl appearing bluish green in daylight and purplish red under incandescent light. Alexandrite has a hardness of 8.5 and is a durable gemstone for jewelry. Top quality alexandrites are rare and valuable.
Alexandrite is also a strongly pleochroic gem, which means it can show different colors when viewed from different directions. Typically, its three pleochroic colors are green, orange, and purple-red. However, the striking color change doesn’t arise from the gem’s pleochroism, but rather from the mineral’s unusual light-absorbing properties. The more significant the color shift from green to red, the greater the value of the alexandrite.
Natural alexandrites with good color change are very expensive and large natural alexandrites are so rare, they are priced well out of reach of most jewelry buyers. Consequently, a considerable market exists for alexandrites that are grown in a labratory. These synthetic stones have the same chemical and physical properties as natural alexandrites. Although the synthetics cost far less than their natural counterparts, they still rank among the most expensive synthetic gemstones available since they are difficult to grow.