Aquamarine and Emerald

Aquamarine, like emerald is a variety of beryl. 

Pure beryl is colourless but as with many gemstones, chemical impurities give gemstones their fabulous colours. Iron is responsible for the beautiful green/blue of aquamarine and minute traces of chromium give emerald its well-loved rich green. 
Aquamarine is loved for its delicate shades of pale blue into aqua. 
Whilst flawless aquamarines are readily available (but expensive), a flawless emerald is rare.
Inclusions in aquamarine are commonly slender parallel tubes known as rain. These are sometimes sought after as information of the gemstone's authenticity.
Inclusions in emerald are also valuable in distinguishing the genuine thing from the synthetic. Often, inclusions in emerald are indicators of the origin of the gem and help to identify its source. For example "three-phase" inclusions are typical of Columbian emeralds.

The most abundant source of aqauamarine is Brazil and the finest emeralds are to be found around Muzo and Chivor in Columbia.
However, there are good emeralds to be found in Sandawana in Zimbabwe, Kitwe in Zambia and Swat in Pakistan.