Green beryl: ligth variety of green beryl. This color is due to Iron Fe2+ & Fe3+. It is oftenoffered as emerald in despite of but it's color is ligther, ussualy with yellow shades.
Yellow beryl: yellow color variety of beryl, it has and greenish tones. But this yellowish beryl is not Heliodor that is the deep golden color variety of berylwhich is named after the Greek words for sun "helios" and gift "doron",much more rare than ligth yellow or yellow - greenish. Unfortunately yellow beryl is named Heliodor in a erroneous way.
Other beryl are:
Aquamarine: blue different shades, blue-greenish.
Heliodor: golden intense .
Emerald: intense green, grass green.
Maxise: deep blue.
Hardness: 7.5 to 8. It is said that aquamarine is harder than emerald.
Specific gravity: medium value 2.72. Highest values are in morganite. Emerald values depends of the origin.
Refraction index: 1560-1594 to 1567-1600. Highest values are in morganite.