1) Corundum gemstone 
Geuda (ගෙවුඩ, pronounced gay-voo-dah) is a form of the mineral corundum, or sapphire, found primarily in Sri Lanka. Around 70%-80% gems mined in Sri Lanka belongs to Geuda varieties. Because of its semitransparent and milky appearance due to TiO2 (Rutile), these stones have little value as gemstones in their natural state. Geuda was freq...