Amador County coal (lignite), although generally low grade in terms of fuel value as compared with bituminous and anthracite coal, commonly
has ptoperties which make it valuable for other putposes. In western Amador County, coal is found solely in the Ione formation of middle Eocene age where it is associated with beds
of clay and sand.
Lignite beds in the Ione region in Amador County were mined for local use early in the 1860's. Intermittent production from this
area continued until 1888, and from this time until 1902, substantial amounts of coal were produced.