Gem laboratories use the word “synthetic” to refer to gemstones created by man but still share the same physical and chemical properties of the corresponding natural gemstone. The same gem laboratory would use the word “imitation” to refer to a gemstone that has different physical properties than the natural counterpart but visually looks similar. 

As with most valuable gem varieties, there are many synthetics that have been made to imitate the Alexandrite. The best and most expensive of these is the lab grown Alexandrite. This material shows the premium color change from teal to red and its change is quite distinct. This material is physically and chemically the same as natural Alexandrite. These gems will cost much more than other imitations, but if you want the look and feel of a real Alexandrite, it is well worth the expense. It is the most desirable, but also the most expensive of the man-made alternatives for Alexandrite.  Beware, if the price is below $20/ct it is extremely unlikely that you are being offered a synthetic Alexandrite.  They are more likely selling synthetic Corundum.