Wood ash is comprised of a variety of chemicals. Mainly consisting of calcium carbonate, it also contains traces of potash, phosphate and other hard metals.
Even though wood ash is mainly calcium carbonate, the composition can vary greatly beyond that point. Composition depends upon the geographical location as well as the process by which the ash was created. Wood ash is composed of key nutrients that the tree leached from the soil during its sapling phase and well into its life. While most hard metals are barely traceable in wood ash, others such as iron, zinc and copper are still detected in some cases.