Learning why slag looks the way it looks

NORTH CANAAN — Intriguing little bits of history can be found all around the Beckley Furnace site.

Chunks of slag, a byproduct of smelting iron from ore, are souvenirs that can be picked up from the ground at what is now essentially a state park full of the history of the great age of iron making. There were three blast furnaces along Lower Road and the Blackberry River.

Pieces of shiny  silicate poke up out of the soil along pathways and the shoreline. During decades of operating the Beckley Furnace, workers dumped the slag just across the river. What now looks like a steep, wooded hillside is actually a 9-acre-wide, 75-foot-deep pile of the glass-like lumps.

At www.beckleyfurnace.org, the newest addition to a video project features a 3-minute tour of the slag pile and the mineralogical components of slag by college student Christian Allyn and directed by high school student Eleanor Jenks,  both of whom are part of a group that promotes the furnace site as a historical and educational gem.

Allyn explains  in the video how various elements color the slag in numerous ways.

Green, from the typical high iron content, is most common.

Aluminum lends shades of light blue and aqua.

Manganese turns the rock purple, with a prismatic effect.

Carbon, from the charcoal burned in the furnaces, turns it black.