Introduction:  Beryl is a mineral species with many well known varieties.  When pure, beryl with a chemical formula Be₃Al₂Si₆O₁₈ is colorless.  Varieties include:

Emerald:  vibrant green beryl colored by chromium, sometimes by vanadium, sometimes by both.

Aquamarine:  blue beryl colored by iron.  Much aquamarine rough when found has a strong green secondary color, caused by a mix of ferrous (blue) and ferric (yellow) iron.  Heat treating results in a blue color and irradiation produces the yellow color.

Green Beryl:  As mentioned under aquamarine above, green beryl colored by iron is sometimes referred to simply as green beryl if left untreated.  To further complicate the nomenclature, green beryl may also refer to a very light green emerald that is not considered dark enough to be called emerald.  As might be expected, there is a great difference of opinion among gemologists, laboratories and dealers as to what is considered “too light”.

Golden Beryl:  yellow to golden beryl colored by ferric iron.  This color can be induced through irradiation of beryl containing iron or it can also happen naturally.  There is no test to separate treated from untreated material.  Alternate names for golden beryl are yellow beryl or heliodor.

Morganite:  pink beryl colored by manganese.  It is typical of morganites when found in nature to be an orange-pink or peach color.  Allowing the stone to sit in daylight for a few days to a week will alter the color to a pure pink.  Heating will have the same result.  There is a new treatment at the time of this writing (2013) that is thought to be a combination of heat and irradiation that yields a dark pink beryl.  At this time, I am unsure of the color stability of this new treatment.

Red Beryl:  an intense red beryl caused by manganese impurities.  Red beryl is also known as bixbite or incorrectly as red emerald, in my opinion.  All red beryl tends to be less than 1 carat and is exclusively from the Wah Wah Mountains in Utah.

Goshenite:  colorless beryl.  This variety has no impurities to impart any noticeable color.

Maxixe Beryl:  an intense blue beryl caused by unstable color centers.  Most Maxixe beryl is produced through irradiation although there is or was naturally occurring material from Brazil.