Natural magic is tapping into the power that is within all living things and expressing that in ways beyond the current understanding of natural laws such as physics and biology. Druidic magic, dragons, monks, elementals and the like are expressions or use this kind of magic.
There are times when Tal itself has such a build up of natural magical energy it is pressurised and solidified into solid chunks of energy. This substance is called Talium. Those trained in the use of natural magic can use Talium for a huge variety of things. Many use it as a direct power source, some use it as a material component for some great spell or rite. Others use Talium to enhance weapons or other items. Talium is valuable but cannot be used as a monetary system as differnet chunks of Talium are different irregular sizes and some of the uses it is put to drains it.
If Talium is not actively used it will retain its energy apparently indefinitely. Importantly talium unused glows. So some use Talium as a lighting system as it will last forever and gives better light than candles.