Emerald

Gem experts differ on the degree of green that makes one stone an emerald and another stone a less-expensive green beryl. Most gemologists, gemological laboratories, and colored stone dealers call a stone green beryl when its color is “too light” to be classified as emerald. Even among that group, however, there’s a difference of opinion about what’s considered “too light.”

TREATMENTS
Several processes are used to alter the color, and apparent clarity, or improve the durability of gems.
SYNTHETICS
Some gemstones have synthetic counterparts with essentially the same chemical, physical, and optical properties, but are grown by man in a laboratory.
IMITATIONS
Any gem can be imitated—sometimes by manmade materials or by natural materials chosen by man to impersonate a particular gem.