The purest mineral available on Sumatra Continent, the king of minerals to build a Human Avatar with, that was Sumatra Gold. Its effects weren't known much, but from his usage of Sumatra Gold, Inala concluded the following points.
First, Sumatra Gold was capable of stabilising the effects of Natures. That was how he could create his Sumatra Lantern with a stable volume of 64 cubic metre while in contrast, all Storage Lanterns could only stably hold a cubic metre without needing constant Prana supply.
Second, Sumatra Gold was immune to all external influences. It was a material inert in all senses. It didn't react to heat, sound, chemicals, and even Prana.
Third, Sumatra Gold was indestructible. Even Maroppa's grey sand was unable to affect it.
Fourth, and the most important point. Sumatra Gold held the Sumatra Continent's presence. Yes, that was it.