Why is volcanic soil so important?

Up on the Bolaven Plateau far back from the main road Lao Mountain Coffee has been supporting the farmers that grows coffee exclusively for LMC (Lao Mountain Coffee).

The green beans that are grown for LMC are Typica, Catimor and Robusta ...The altitude for the The Typica and Catimor is above 1200 meters above sea level where as the Robusta is above 1000 meters above sea level.
The Typica Arabica beans is very limit to grow on the Bolaven Plateau due to the fact that certain area the volcanic soil is not suitable for growing.
Where as the Catimor Arabica is grown mainly on the Bolaven because it not prone to rust disease..Rust disease is a foliar disease of coffee plant cause by fungus...The Catimor is a hybrid of Arabica and Robusta is not prone to the Rust disease. T
o grow good green beans you need good rainfall,cool temperature and rich volcanic soil. All your best green beans for coffee is grown on Volcanic soil. Volcanic soil is rich in nutrients like zinc cholrine, iron,nitrogen,boron and hold alot of water to make the soil more fertile.