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The surface of the earth has existed for hundreds of millions of years. During that time, it has undergone many changes. Sometimes landlocked bodies of water evaporate and leave behind their dissolved minerals. You might think that such deposits would be salty, but as we will see below, there are many other possibilities.
Notable evaporites: From borax to polyhalite in Yorkshire
Notable evaporites: From borax to polyhalite in Yorkshire
When minerals come out of solution like this from an evaporating body of water, the resulting material is called an "evaporate."
One well-known evaporite is borax (sodium borate), which many may recognize from the boxes featuring a 20-mule team wagon train. Borax formed from evaporating lakes in what is now the Mojave Desert in California during the Miocene epoch, around 10 to 5 million years ago. It's used in household cleaning products, as a water softener, and in various industrial applications.
Another prominent evaporite is gypsum (calcium sulfate). Gypsum deposits are found all over the world. One of the largest is in the White Sands National Park in New Mexico, where vast dunes of gypsums sand, sifted and piled by the wind, provide breathtaking views. Gypsum is used to make plaster and drywall, and has been used for centuries in construction and art (as well as for casts, traditionally, when you break your arm).
An example of a less common and more valuable evaporite is lithium-rich hectorite, mined primarily in the Mojave Desert, California, and in some regions of Nevada and Wyoming. These deposits formed in at the bottom of saline lakes that evaporated in the Pleistocene epoch, around 2.5 million years ago. Used in the production of lithium batteries, cosmetics, and as a drilling mud additive in the oil industry, hectorite's unique properties and scarcity make it a high-value mineral.
Polyhalite in Yorkshire
Polyhalite in Yorkshire
The polyhalite found deep underground in Yorkshire, England, was among the last of a long sequence of evaporates. This polyhalite, a mineral consisting of potassium, calcium, magnesium, and sulfate, was formed during the late Permian period, around 260 million years ago. In my vision, I was transported back to that time, when the Zechstein Sea covered much of what is now northern Europe, repeatedly evaporating and refilling, leaving behind layers of different combinations of evaporites.
The outlines of the former Zechstein Sea basin are shown on the map below. This was during the Late Permian period, in Earth's ancient geological past, long before the continent of Europe would take its familiar shape. The Zechstein Sea's borders, as marked, roughly correspond to regions that today include the North Sea, extending across parts of the UK, Netherlands, Germany, Poland, and beyond.
Outer limits of the Permian Basin containing the Zechstein Sea,late Permian Period
The evaporative phases of the Zechstein Sea
In the vast area covered by Zechstein Sea long ago, the sea's waters rose and fell through natural cycles lasting in total for about 5 million years. During that time, the Zechstein Sea experienced around a thousand evaporative phases, grouped into five major cycles. It's within these cycles that the magic mineral formation of polyhalite occurred.
Close-up of organic polyhalite crystals fringing the Zechstein Sea, near feet of large therapsid (late Permian Period)
In my vision, this process was not just a concept, but a vivid reality. I witnessed the polyhalite forming under the water, crystallizing and building up as part of the sea floor, echoing the natural ebb and flow of an ancient and cyclical world. It was during one such phase, amidst these transformative cycles, that I encountered the empathetic therapsid. She was radiating benevolence, and seemed to be telling me that the white mineral around her was somehow important, bridging millions of years in a single, profound moment of connection.
Modern times
Fast forward hundreds of millions of years, to the times when humans first migrated to Europe. Then, for millennia, the secrets of the Zechstein Sea lay hidden beneath the European landscape, unknown to the burgeoning civilizations above. In Yorkshire, England, the polyhalite formed by those ancient seas was buried deep, nearly a mile under the surface. This treasure trove of minerals lay in silence, undisturbed and undiscovered, as life evolved and human history unfolded overhead.
It wasn't until modern geology began to probe the depths of the Earth that the existence of this polyhalite came to light. Geologists, through a combination of surveying techniques and scientific curiosity, identified this buried layer of minerals. Their discovery was not just a stroke of luck but the result of meticulous study and exploration of the subterranean world.
Once brought to the surface, the polyhalite required further study. By grinding it into a powder and testing its effects, researchers and agronomists found that it was incredibly beneficial for crops. Polyhalite stood out as a multi-nutrient fertilizer, offering a gradual release of the macronutrients potassium, magnesium, calcium, and sulfur along with various micronutrients. It is being used more and more around the world to make soils healthier and crops more abundant.
Man scattering organic crop nutrients, which will enter the soil to nourish the crops
Plants need to eat too! They get carbon dioxide from the air, they get H₂O from the air, but they also need many other elements like sulfur for proteins, magnesium for chlorophyll, phosphorus, potassium, etc. When the soil gets low in these elements, they love it when someone can add organic fertilizers like polyhalite to nourish them. Polyhalite is also good for the soil microbiota (beneficial bacteria, fungi, worms, grubs, tiny crustaceans, and myriad other creatures that live in the soil). And because its extraction and processing have a lower carbon footprint compared to other mineral fertilizers, it is a climate-friendly option. So it's no coincidence that the empathetic therapsid in my vision was transmitting enthusiasm about the polyhalite crystals that were forming all around her, communicating its importance for our era.
Next section:"Composition and Qualities"
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Credits:
Map showing boundaries of ancient Permian Basin: Open access image from https://www.mdpi.com/2076-3417/12/14/7183
Depiction of polyhalite deposit fringinging ancient Zechstein Sea: John Norman in collaboration with Dall-E
Man scattering crop nutrient: Image credit: Playaelyaque, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
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