Most of the big, stunning crystals that we find   on Earth are the end result of  millions of years of formation.

They grow deep in the Earth’s  crust in tectonic processes,   or on the Earth’s surface in sealed caves, in  both cases taking eons to form and be found. But there’s one collectible crystal  that sometimes forms a lot faster.

In a windswept desert along the coast of Qatar,   gorgeous formations of desert rose are created  in a matter of decades, right beneath our feet. [♪ INTRO] Desert rose crystals are common  sights in museum gift shops. They’re named, somewhat uncreatively, for  their rose-like appearance and sandy texture. What sets them apart from all of the shiny  faceted specimens on the shelf is that the   desert rose isn’t technically mineral  at all, but a combination of minerals.

It’s made from flattened crystals of evaporite  minerals, like gypsum or barite, that have grains   of quartz peppered through them like chocolate  chips in a muffin, only a lot less tasty. Please don’t eat the desert rose. Now, normally, minerals combined together  like this would be classified as a rock,   but rocks don’t have a predetermined shape.

And although the shape of that rock  formation can vary, we always find   this combo as bundles of these flattened crystals. So desert rose is really  neither a mineral nor a rock. It’s its own unique thing, with  a unique formation process.

It starts with evaporites. As their name suggests, these are minerals  that form when saline waters evaporate. Common table salt, which in the  mineral world is called halite,   is technically an evaporite, and there are  more than 100 other types of evaporites too.

One group have sulphates in their  mineral structure, and are pretty   stable over long periods, and it’s these  that form the basis for desert roses. For instance, gypsum is calcium  sulphate with a bit of water mixed in,   barite is barium sulphate, and  celestine is strontium sulphate. Which mineral you get depends on the specific  chemistry of the water you’re starting with,   and how much of that water has already evaporated.

Evaporating water forms a succession  of minerals in order of solubility,   with the least soluble - like calcium  carbonate, precipitating out first,   and the most soluble, like  halite, precipitating out last. The sulphates fall somewhere in  the middle of this succession,   but you have to shift a fair  bit of water to get at them. For instance, to get just 1cm thickness of gypsum,   you’d need to evaporate 25  meters of normal seawater.

But making evaporites is only  half of the desert rose story. In order to create the distinctive sandy  texture, the evaporite minerals need   to begin growing in the pore spaces of  existing sandy sediments or sandstones. So, as the crystal grows, it swallows up the sand  grains and incorporates them into its structure.

Gypsum and barite naturally form tabular  crystals, which become the flattened petals   of the rose, and when these all start  growing from a single central point,   they end up radiating outwards to form a  unique and distinctive three-dimensional shape. The flattened barite crystals  extend outward from their edges,   and organic matter inside the sediment is  thought to interfere with their growth,   rounding off the corners to make the petals  rounded, enhancing the rose-like appearance. Now, given that the raw ingredients of desert  rose are essentially salty water and sand, we can   theoretically find them wherever these two coexist  for long enough for that water to evaporate.

This isn’t as easy as it sounds, though  - you’re not going to find them on your   average sandy beach, because water doesn’t  stick around there long enough to evaporate. Instead, desert rose specimens are  often found in unexpected places   like the famously dry Sahara, the Chihuahuan  desert of Mexico and, remarkably, Oklahoma! The residents of Oklahoma were so  taken with their crystal bounty that   the desert roses there, made of barite,  have been named the official state rock.

And they’ve been created without any  input from the salty seas at all. Instead, brines are thought to have  risen up from deep inside the crust,   as a byproduct of organic  matter being cooked into oil. These brines penetrated the 250  million year old Garber sandstone,   flowing through cracks in the Permian  rock and evaporating very gradually,   allowing barite to grow and desert  roses to form around those cracks.

As the ancient sandstone is uplifted,  it’s weathered back into sediment,   but the desert roses survive, popping  out like actual flowers on the surface. Because all of this happened deep  underground, scientists don’t have a   very good idea of exactly when the  desert roses of Oklahoma formed. We know they must be younger than the 250  million-year-old sandstone that hosted them as   they grew, but the other processes still point  to a process lasting many millions of years.

Oil and its associated brine  takes millions of years to cook,   water will evaporate incredibly  slowly while it’s still underground,   and then it’ll take millions of years more for  the sandstone to be uplifted and weathered. All of that points to an ancient state rock that,  like most other rocks, is a product of eons. Oklahoma, I would shame you for  making your state rock… not a rock.

But we putting this in the “Rocks Box,” so  I actually don’t think we have room to talk. However, in one part of the Arabian peninsula,  very similar specimens are being created under   very different circumstances that  have fast-tracked their formation. Like much of Arabia, the landscape  of Qatar is dominated by deserts,   and if you take a stroll along  some of the deserts near the coast,   there’s a good chance you’ll stub your toe  on desert roses right there at the surface.

These coastal environments  are what’s known as sabkhas:   coastal salt flats whose landscape is dominated  by alternating flooding and evaporation. In southwestern Qatar in particular, the  Umm Said sabkha stretches for more than   30 kilometers along the coast of the Persian gulf,   and it’s here that some of the most remarkable,  modern desert roses are found, made of gypsum. Researchers think that the hot, dry climate boosts  evaporation of water from the sabkha’s shallow   water table, which then pulls salty water  into the groundwater from the nearby ocean.

With constant evaporation  and constant salty resupply,   the levels of dissolved salts in the  groundwater here can become extremely high,   allowing evaporite minerals to precipitate and  desert roses to form right at the water table. Now, the conditions need to be  just right for this to happen. Too close to the sea, and the groundwater  will be diluted by lower salinity water.

Too far, and the seawater  won’t be pumped in at all. And the level of the water table is important too. It seems like the desert roses  crystallize when the water table   is between half a meter and one and  a half meters below the surface.

If it’s deeper, then the evaporation  isn’t strong enough to form gypsum. And if it’s shallower, the evaporation  is so strong that a salt crust forms,   and stunts the growth of roses. But across the sabkhas of Qatar,  these conditions are all met,   to help desert roses grow just below the surface.

Then, as the desert winds blow the surface  sand away, the treasures are exposed. Unlike the roses of Oklahoma, which were formed   by millions of years old brine inside  hundreds of millions of years old rock,   it’s thought that these Qatari desert  roses take just a few decades to form. Which is basically nothing in geological terms!

Not only are they modern creations, but they’re  constantly being renewed by salty water from   the Arabian gulf, making this unique desert  environment a crystal factory for desert roses. This month, SciShow Rocks Box  subscribers will receive their   own crystal flower in the mail,  all the way from sunny Oklahoma. Every month, Rocks Box subscribers get a piece  of our planet’s geological record, whether it’s   a mineral, a fossil, or a multi-layered  evaporite crystal, which is… not a rock.

If you want to learn more, head over  to SciShow. Rocks and check it out. We also have a few a la carte minerals  to peruse along with other merch.

Thanks for watching! [♪ OUTRO]