Emerald simulants are something that looks like an emerald, but does not share any of its physical or chemical properties. Not to be confused with a synthetic emerald, which is a man-made emerald. This also means stones like peridot, green garnets, or other green gems historically confused with emeralds can be emerald simulants as well. Many emerald simulants also have names tagged onto the term emerald. For example, “Endura emerald” is another name for green glass. Not the precious gem.
Emerald simulants have a long history dating back to the Greek. Both Pliny and Seneca (~ 1st century) mention the practice of staining stones to imitate smaragdus. The Papyrus Graecus Holmiensis, which is also known as the Stockholm Papyrus (recorded in the 3rd or 4th Century A.D.) provides 1st century recipes for imitating precious stones.
The Egyptians were proficient with glass for jewelry, and there are descriptions of quartz being cracked from rapid cooling (from a furnace to a bucket), then dyed green by Indian dealers. C. W. King (1865) described how clever dealers in Ceylon used the bottom of wine bottles to create fine “emeralds,” then sold at high prices to foreigners.
A more recent type of simulant is to take two pieces of colorless gem and stick them together with colored glue. These are referred to as assembled gems, in addition to being simulants. This is not to be confused with the practice of assembling genuine opal with a backing and/or glass to make them durable enough to be set.
Pieces of the assembled emerald simulant may be colored green, and the glue is colorless, or there is just a thin sliver of emerald on top to try and fool a gemologist. Assembled gems are also some of the easiest simulants to identify since there is a glue border around the edge, and maybe a colorless section visible from the side depending on the assembled gem. Sometimes there is just a beryl cap on a piece of green glass, though the border between the two is often visible in reflected light. Basic magnification at 10 times normal vision makes these features very apparent too.