Coal
Indonesian thermal grade steam coal has a soft texture, is black and lightweight and is known to be of far superior quality compared to Indian coal.
Coal quality can be measured in GAR (Gross As Received), ARB (As Received Basis) or GCV (Gross Calorific Value, measured in Kcal/Kg), which are essentially the different names for the same metric. In Indonesia, GAR is the most common and basic metric used to measure coal quality.
Indonesia has abundance of low to medium grade, but high quality coal. The range goes from 3400 GAR to all the way upto 6500 GAR. Indonesian coal is superior to Indian coal in terms of having very low Ash and Sulfur content. For example, average Indonesian coal has an ash content below 3%, while Indian coal could have ash content anywhere around 30%.
Other than above grades, Indonesia has some reserves of 7000+ GAR as well, which is also known as coking coal. It is mainly used for metallurgical processes, for e.g. in steel industry.