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I want to have a blue furred species native to a desert in the world I'm building, so the obvious way to have that is to have the sand of that desert be blue so they are camouflaged. I could just say the sand is blue and be done with it, but I'd rather have an explanation for why the sand is blue.

So, what would be a way to have blue sand on an alien planet, probably a mostly desert planet?

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You want BLUE SAND?

I've got your blue sand on special today, available in the hundreds of thousands of hectares in sunny Namibia.

And we are not talking those feeble green-pretending-to-be-blue sands of Taiwan, or even the occasional dark blue flacks from Colorado. This is the Genuine Real Deal Blue Sand
(image is 15mmx15mm)

enter image description here (Source)

Here is the same sand, before it gets broken up into sand.
enter image description here

P.s. Just for funsies: Under UV light this stuff glows in bright neon Orange and Red shades.

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    $\begingroup$ But does a dune field of it actually look blue from a distance? I don't see a picture of a pile of it viewed from a distance where you can't see the grains. $\endgroup$ – Mark Foskey Jan 9 at 20:22
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    $\begingroup$ @MarkFoskey It is only about 2% of the sand. Natural filtering by the wind makes contours of these around the edges of dunes, from above it looks almost like oil slick. But all that's needed is a region where the relative abundance of that mineral is a lot higher (added suitable image above). And yes, the dry sand looks a soft baby blue. Wet, it shades almost to indigo. But sand there is very, very rarely wet. $\endgroup$ – PcMan Jan 9 at 20:56
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    $\begingroup$ @bradrn because a freshly-mined sample is all nice and clean, pretty with sharp edges and uniform grain size? Whereas the stuff out in the dirt is... well, dirty. All scuffed up and eroded by wind and dust and muck. $\endgroup$ – PcMan Jan 10 at 6:13
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    $\begingroup$ @bradrn That photo is from a cleaned, prepared tourist specimen. Yes, it is not natural, I'm pretty sure that natural sand does not come pre-prepared in round polycarbonate containers with a $18.95 price tag attached. It was selected because it clearly shows the composition and color of the specimen. Take a look at 6the other picture I supplied, that shows the rock the sand of formed from. Or, as you seem to not believe other people's facts. Go out to Namibia and walk the dunes near Swakopmund. If the DeBeers diamond mine guards don't shoot you, you can see these sand for yourself, as i did. $\endgroup$ – PcMan Jan 10 at 9:03
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    $\begingroup$ @PcMan Sorry, I misinterpreted your earlier comment. Of course I am aware that the specific image you linked is a prepared specimen — the sand itself could not possibly be so clean! I was simply quoting the article, which speculates that this occurrence of blue sand may have been originally created by human activities — in this case, sodalite mining — and so could not have been present before Western colonisation of Namibia. [1/2] $\endgroup$ – bradrn Jan 10 at 21:31
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For certain minerals the size of the particle or the presence of defects affect its color, due to how the light interacts with the material.

For example titanium dioxide appears to be light blue.

natural TiO2 is always bluish. This is because natural TiO2 is always contains considerable oxygen vacancies that result reduced TiO2. The vacancy state turn as Ti3+, and creates an in-gap state and form an intermediate band just below the conduction band of the host material.

If your sand is mostly TiO2 based rather than SiO2 based that can be an explanation.

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    $\begingroup$ You might also consider Egyptian Blue, which is a bright blue silicate compound. $\endgroup$ – Joe Bloggs Jan 9 at 9:48
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    $\begingroup$ The species might use blue camouflage against the sky. $\endgroup$ – Slarty Jan 9 at 10:38
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    $\begingroup$ Titanium dioxide bags I have in front of me is varying between white and light grey. No blue tint at all. It looks like ebay.com.au/i/201969588647. (It's a pigment and also used in sunscreen, which is usually white.) $\endgroup$ – Ash Jan 9 at 16:07
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    $\begingroup$ @Ash, it depends on the processing conditions and grain size (the link provide more info). I used TiO2 to build DBR ranging from blue to red $\endgroup$ – L.Dutch - Reinstate Monica Jan 9 at 16:23
  • $\begingroup$ @L.Dutch-ReinstateMonica - "DBR" - is it this?: en.wikipedia.org/wiki/Distributed_Bragg_reflector $\endgroup$ – IronEagle Jan 9 at 21:34
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There's a certain type of rock called blueschist:

enter image description here

The blue colour is coming from a mineral called glaucophane:

enter image description here

This is a rock type that is usually found in mountain belts, not far away from the coast. The problem is that the mineral itself (glaucophane) tends to break down very easily when it's exposed to the elements (beach waves, rivers, etc). But very close to the mountains, maybe immediately below a cliff or something, it is realistic to find blue sand derived from these rocks. The fact that you want it to be in a desert helps. But don't make it the only type of sand - yellow/white quartz sand is still going to be the most common. Just that in some places, you might find glaucophane sand that results from breakdown of nearby blueschists.

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It does not need to be blue if it looks blue.

reflective salt

https://steemit.com/travel/@sagor24/reflective-salt-flats-in-bolivia

These salt flats make mirages all the time, and when it rains the film of water is like a mirror. You could use a salt flats for your desert or something similar. Your creatures are not flat blue but an agouti blend of light blue dark blue and white, which will be great when they make your story into an anime.

Blue sand is cool but this place is positively surreal and would be wonderful for a fiction. Shout out to @Slarty who proposed your creatures camouflage against the sky which is what they would be doing.

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All of the other answers are good.

I want to have a blue furred species native to a desert in the world I'm building, so the obvious way to have that is to have the sand of that desert be blue so they are camouflaged. I could just say the sand is blue and be done with it, but I'd rather have an explanation for why the sand is blue.

There are lots of reasons there might be a blue-furred animal. Saying it's to camouflage with a desert will require lots of blue sand, but that's ok because there are lots of reasons why the sand might be blue.

If you're trying to tell a story, consider how deep into this you really want to go.

Also consider from the other angle: Why aren't there blue-furred animals on earth? Why might those reasons not apply on some other planet?

I don't have a great link for this; here's something. Basically, making a molecule that's inherently blue and is stable in an animal's body is pretty hard. The best way to shift this balance is probably to supply a relative abundance of metals and natural non-biologic blue pigments in the environment, i.e. have there be lots of blue rocks.

Basically, where X is whatever blue mineral or minerals,

  • Animals are blue (or able to be blue pending evolutionary pressure) because they have traces of X in their diet.
  • The X in their diet comes from sand/grit from the local geology.
  • The local geology has lots of X in it (and is therefor relatively blue) because that's just how that region of that planet is. You can chase it up to stellar phenomena billions of years prior, but to what end?
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The sand doesn't need to be blue if the primary species they deal with are all colorblind. Good color vision is somewhat rare; deer for example can't see orange on green all that well, so hunters can wear high-vis orange without worrying about getting spotted. Blue-green color blindness is something that occurs in humans, and alien creatures can have a completely different visual system.

They could also be nocturnal, (common in deserts) at which point color vision becomes even worse, and dark blue is a reasonable camouflage to use on anything that doesn't specifically have night vision.

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Surprised there hasn't yet been an honourable mention of two amazingly coloured blue birds that appear in nature via different methods without their surroundings being blue. Fair enough if you want blue sand, but here's justification for an alternative:

Blue-footed Booby:

The blue color of the blue-footed booby's webbed feet comes from carotenoid pigments obtained from its diet of fresh fish.

Hummingbirds:

When sunlight hits these [prismal cells], it is split into wavelengths that reflect to the observer in varying degrees of intensity, with the feather structure acting as a diffraction grating.

Both methods seem to feature carotenoid-based pigmentation obtained from the birds' diet (also the same for flamingoes too), though the fur/feathers/scales of your creature splitting and refracting light so that it appeared blue to the viewer is a cool world build.

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  • $\begingroup$ The original question is not about how the animal is blue, but rather, about why it would be blue. $\endgroup$ – João Mendes Jan 11 at 13:44
  • $\begingroup$ Would you like to add a blue banded bee into the mix & how about a blue dog? $\endgroup$ – Fred Jan 12 at 9:30

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