[Sunandsand123 (OP)]

Hello,

53179982_10156130166386765_7968750658775941120_n.jpg (203.52 kB . 790x960 - viewed 9604 times)

I live in Saudi Arabia and we went out in the desert to look for Sand Roses and I don't know much about them...

We found a fair few, but some of them are crumbling...do they last? How long? How can I keep them forever intact?
I seem to have read that they are made from Gypsum or Baryte and that the gypsum ones tend to be more fragile..I washed the sand off of them and so did my friend. I know because there is mineral in it and that these types of rocks might be "alive" and therefore transform with time, with weathering, light etc. But I want to keep my roses :/....can anyone help me??  Thanks in advance!

[chris]

I'm so glad you asked this question because I have vivid memories of my parents having one of these in their "rock cupboard" at home; I never knew what it was!

Now we await the geologists @Bass who can actually tell us more about them!

[evan_au]

These appear to be members of a class of minerals called evaporites - formed by evaporation of water from temporary lakes, leaving behind crystals of the minerals that were previously dissolved in the water.
- So washing the sand out is probably not a good idea, as that will dissolve some of the mineral back into the water.
- Next time try blowing the sand out with a gentle flow of air...

See: https://en.wikipedia.org/wiki/Evaporite

[Bass]

Welcome to the forum Sunandsand123. You found some nice specimens.
Known as "desert roses", "sand roses" and "selenite roses", these are actually gypsum (calcium sulfate dihydrate- calcium sulfate with water molecules attached). These form in arid environments, and as you've discovered are very fragile.
Evan-au correctly pointed out that using water (hydrating) the rosettes will cause them to break down more quickly- so try to keep them dry in place where they won't be jostled around.
Barite (baryte) roses form from barite (barium sulfate) which tend to be both harder and more durable than gypsum roses.

[Bored chemist]

Probably as good a way to "stabilise" them as any is to  put them in a closed container so they can't lose or gain water from the air.

Something like this
https://www.marksandspencer.com/bell-jar/p/p60115718
(I have no sensible idea of the scale of your specimens or the bell jar- but they are available in many sizes.)

[Bill S]

As commented above, keeping these specimens dry is the best thing.  Some may be a lot less "hardy" than others. I have a couple of beautiful examples from the Sahara, together with some local (Essex) selenite crystals. They have survived, unprotected, in the relatively damp UK atmosphere for 50 years, many of those, in a box in the loft.

[Bored chemist]

It's true that water will dissolve selenite.
But it's also important to recognise that the crystals have water as part of the structure. If they dry out they will crumble to dust.
I'm not sure how dry that needs to be. Presumably, very dry- given that you find them in deserts.

[Bill S]

Obviously the “desert roses” came from the desert, but the selenite crystals were from the London Clay at Wrabness

http://www.essexfieldclub.org.uk/portal/p/Geology+Site+Account/s/Wrabness+London+Clay+Cliffs+(part+of+Stour+Estuary+SSSI)/o/Wrabness+London+Clay+Cliffs+(part+of+Stour+Estuary+SSSI)

back in the days when it was possible to extract good specimens there.

[Monox D. I-Fly]

These appear to be members of a class of minerals called evaporites - formed by evaporation of water from temporary lakes, leaving behind crystals of the minerals that were previously dissolved in the water.
- So washing the sand out is probably not a good idea, as that will dissolve some of the mineral back into the water.
- Next time try blowing the sand out with a gentle flow of air...

See: https://en.wikipedia.org/wiki/Evaporite

So... To put it in Layman's Terms, they're Desert Salt?