Each and every gem families has spesic features.according to that tourmaline is a family.tourmaline is colourful family.but in sinhala mangu is called dravite tourmaline.because which is abundantly found in dravite valley. I'm not a gemologist.but I also research about gemstones.by the way of mine your videos and teaching is very helpful to me.I also saluite to you,sir.because most of dealers are trying to cheat customers and miners,but you teach for us what is the true and real.secondly I saliute to you.remember I'm not a GEMOLOGIST.