The coal industry of Maverick County is located along a section of the Olmos Coal Formation immediately north of Eagle Pass. Mining operations developed by Dolch at Dolchburg and by the Olmos Coal, Coke, and Oil Company at Olmos were the largest coal producers in Texas around the turn of the 20th century.
Those photos still fade over time, plastic doesn't prevent the materials from fading or deteriorating. Pencil that's the old lead pencils, or the new graphite pencils will not fade. Graphite is the most stable form of carbon. It's color is grey rather than black, so the line will be lighter than a black color pencil, but they are not susceptible to fading, they are extremely stable.
Lead pencils, of course, contain no lead. The writing medium is graphite, a form of carbon. Writing instruments made from sticks cut from high quality natural graphite mined at Cumberland in England and wrapped in string or inserted in wooden tubes came into use around 1560. [1] The term black lead pencil was in use by 1565. By 1662, pencils were produced in Nuremberg, in what is now Germany, apparently by gluing sticks of graphite into cases assembled from two pieces of wood.