The Woodsmith Project will be the UK’s biggest mining operation, located on the North Yorkshire coast near Whitby and on Teesside. Since its inception almost a decade ago, this project has been dedicated to the unearthing of polyhalite, an evaporite mineral that lies over a mile underground.
Polyhalite is composed of potassium, sulphur, magnesium and calcium molecules, four of the six elements that plants need to grow. This makes it an ideal natural fertiliser, able to improve arable soils and crop yields in an efficient and environmentally friendly way, at a time when farmers worldwide are under pressure to produce more crops in a more sustainable way.
But what is polyhalite, where did it come from, and how did it get here?
The origins of the Woodsmith Project’s polyhalite deposit can be traced back as far as the Permian Period, the final stage in the Paleozoic Era. The story of our project is approximately 250 million years old, older than homo sapiens or even dinosaurs.
At this point in pre-history, what we now know as North Yorkshire looked very different. The Earth’s continents were fused in one giant landmass called Pangaea, a supercontinent centred around the equator. The fusion of Pangaea had triggered a period of global warming and a dry, arid climate. It’s hard to imagine today, but what is now rainy northern England was then a desert basin, dotted with salt lakes and sweeping sand dunes.
Pangaea and the Extension of Zechstein Sea, Central Europe, 255 million years ago
Over time however, ice sheets in Southern Pangaea began to melt, causing sea levels to rise and forming an inland body of water called the Zechstein Sea. Over the next seven million years, it periodically evaporated, leaving behind the salts found in its seawater. It is these ancient marine salts which form the polyhalite deposit we know today. Indeed, the name polyhalite literally means “many salts”. Geologists suggest that this process of evaporation happened thousands of times over five main cycles, building multiple mineral layers over millions of years, in a huge succession stretching from northern England under the North Sea as far as northern Germany and Poland.
Although polyhalite was first identified in the 19th century, its presence in North Yorkshire wasn’t discovered until the 1930s when geologists began exploring the region in search of hydrocarbons and sylvite, another evaporite mineral used to make potash fertiliser. The presence of a large deposit of polyhalite was noted but, having found the oil, gas and sylvite that they were looking for, its commercial potential was overlooked. It was not until 2011 that a prospecting company, which later became the Woodsmith Project, used this data as a basis for futher exploration, enabling the identification of a polyhalite resource of over 2 billion tonnes (the largest known high-grade polyhalite deposit in the world) and in-turn the promotion of its use as an effective, slow-release multi-nutrient fertiliser – POLY4.
In exploring, extracting and spreading polyhalite around the world, we are adding another intriguing layer into the 250-million-year-old story of polyhalite.