The Origin of Ochre (Part One)

 In our last installment, we learned how an ochre mine in Forestdale may have been home to a giant frog discovered in 1865.  So what is ochre anyway? And why was it being dug up?  Basically, ochre is a clay-based rock that contains iron oxide, aka rust. It produces colors from red to yellow when pulverized, which is easily done because it softens  quickly with water.  Native Americans used ochre for body paint, to decorate pottery, and in burial ceremonies.  Early European residents of Brandon also used ochre for paint, which was made on, you guessed it, Paint Works Road.

So why is there ochre in Forestdale?  Clay is made when certain types of rocks break up into very fine particles, are washed away by moving water, and settle in layers when the water slows down or stops moving.  The story of Forestdale’s ochre takes us back 1.3 billion years ago on the part of the globe where South Africa sits today, with a continental collision.  As we’ll see later, collisions between continents aren’t entirely unlike collisions between cars, and this collision was something of a hit-and-run.


Geologists call these very early continents “cratons”, and refer to the craton that forms the core of current North America as “Laurentia”.  So a billion years before dinosaurs showed up, Laurentia was floating around somewhere south of the equator when another continent collided with it.  No insurance information was exchanged, and all traces of the other continent have been lost, but the collision left Laurentia with a Himalaya-sized crumple that we now call the Adirondacks.  Some folks claim the colliding continent was South America, but the scientific community is divided on this account and any evidence may have been damaged in more recent collisions.  Whatever continent was involved drifted off again, leaving oceanic crust to fill the gap, underneath a tropical sea.


Unlike Vermont, much of which is built on granites and marbles, the Adirondacks are largely made out of bedrock containing iron. American icons such as the Brooklyn, Golden Gate, and George Washington bridges are all made out of Adirondack iron.  Over hundreds of millions of years, the Adirondack mountains eroded from an original height of over 25,000 feet, down to their current heights between 4000 and 5300 feet.  The ochre in Brandon originated not in our beloved Green Mountains, but is a leftover from when Vermont was essentially a foothill of the mighty Adirondacks.






Later continental collisions would raise the Taconic Mountains, the Green Mountains, and eventually the White Mountains. Not unlike a highway car pile up, these later crashes can be sequenced by their place in line.  From west to east, the Taconic collision happened at 440 million years ago, the Green Mountains at 345 million, and the Whites at a mere 136 million years before present.

In our next installment, we'll learn more about how and why ochre was mined in Brandon.

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