In this article we return to the roots of the Caledonian mining tax system. We aim to find out what principles have structured its implementation and its development. We highlight the key elements of the Caledonian mining tax system based on legislation since 1859 and public budget data since the 1900s. After some trial and error, the yields from the mining claims and the proportional taxation on mining exports became the main tools of the Caledonian mining tax system. However, since 1975, taxation on the profits of mining companies has replaced taxation on mining exports –which has increased the instability in Caledonian tax revenues.